使用 O(1) 额外空间在交替的正负项中重新排列数组 |设置 2
给定一组正数和负数，以交替方式排列它们，使每个正数后面跟着负数，反之亦然。输出中元素的顺序无关紧要。额外的正面或负面元素应移至结尾。
例子：
Input :
arr[] = {-2, 3, 4, -1}
Output :
arr[] = {-2, 3, -1, 4} OR {-1, 3, -2, 4} OR ..
Input :
arr[] = {-2, 3, 1}
Output :
arr[] = {-2, 3, 1} OR {-2, 1, 3}
Input :
arr[] = {-5, 3, 4, 5, -6, -2, 8, 9, -1, -4}
Output :
arr[] = {-5, 3, -2, 5, -6, 4, -4, 9, -1, 8}
OR ..方法一：
- 首先，以非递增顺序对数组进行排序。然后我们将计算正整数和负整数的个数。
- 然后在奇数位置交换一个负数和一个正数，直到达到我们的条件。
- 这将重新排列数组元素，因为我们正在对数组进行排序并根据需要从左到右访问元素。
下面是上述方法的实现：
C++
// Below is the implementation of the above approach
#include
using namespace std;
// Function which works in the condition
// when number of negative numbers are
// lesser or equal than positive numbers
void fill1(int a[], int neg, int pos)
{
if (neg % 2 == 1)
{
for(int i = 1; i < neg; i += 2)
{
int c = a[i];
int d = a[i + neg];
int temp = c;
a[i] = d;
a[i + neg] = temp;
}
}
else
{
for(int i = 1; i <= neg; i += 2)
{
int c = a[i];
int d = a[i + neg - 1];
int temp = c;
a[i] = d;
a[i + neg - 1] = temp;
}
}
}
// Function which works in the condition
// when number of negative numbers are
// greater than positive numbers
void fill2(int a[], int neg, int pos)
{
if (pos % 2 == 1)
{
for(int i = 1; i < pos; i += 2)
{
int c = a[i];
int d = a[i + pos];
int temp = c;
a[i] = d;
a[i + pos] = temp;
}
}
else
{
for(int i = 1; i <= pos; i += 2)
{
int c = a[i];
int d = a[i + pos - 1];
int temp = c;
a[i] = d;
a[i + pos - 1] = temp;
}
}
}
// Reverse the array
void reverse(int a[], int n)
{
int i, k, t;
for(i = 0; i < n / 2; i++)
{
t = a[i];
a[i] = a[n - i - 1];
a[n - i - 1] = t;
}
}
// Print the array
void print(int a[], int n)
{
for(int i = 0; i < n; i++)
cout << a[i] << " ";
cout << endl;
}
// Driver code
int main()
{
int arr[] = { 2, 3, -4, -1, 6, -9 };
int n = sizeof(arr) / sizeof(arr[0]);
cout << "Given array is ";
print(arr, n);
int neg = 0, pos = 0;
for(int i = 0; i < n; i++)
{
if (arr[i] < 0)
neg++;
else
pos++;
}
// Sort the array
sort(arr, arr + n);
if (neg <= pos)
{
fill1(arr, neg, pos);
}
else
{
// Reverse the array in this condition
reverse(arr, n);
fill2(arr, neg, pos);
}
cout << "Rearranged array is ";
print(arr, n);
}
// This code is contributed by Potta Lokesh Java
// Below is the implementation of the above approach
import java.io.*;
import java.lang.*;
import java.util.*;
public class Main {
// function which works in the condition when number of
// negative numbers are lesser or equal than positive
// numbers
static void fill1(int a[], int neg, int pos)
{
if (neg % 2 == 1) {
for (int i = 1; i < neg; i += 2) {
int c = a[i];
int d = a[i + neg];
int temp = c;
a[i] = d;
a[i + neg] = temp;
}
}
else {
for (int i = 1; i <= neg; i += 2) {
int c = a[i];
int d = a[i + neg - 1];
int temp = c;
a[i] = d;
a[i + neg - 1] = temp;
}
}
}
// Function which works in the condition when number of
// negative numbers are greater than positive numbers
static void fill2(int a[], int neg, int pos)
{
if (pos % 2 == 1) {
for (int i = 1; i < pos; i += 2) {
int c = a[i];
int d = a[i + pos];
int temp = c;
a[i] = d;
a[i + pos] = temp;
}
}
else {
for (int i = 1; i <= pos; i += 2) {
int c = a[i];
int d = a[i + pos - 1];
int temp = c;
a[i] = d;
a[i + pos - 1] = temp;
}
}
}
// Reverse the array
static void reverse(int a[], int n)
{
int i, k, t;
for (i = 0; i < n / 2; i++) {
t = a[i];
a[i] = a[n - i - 1];
a[n - i - 1] = t;
}
}
// Print the array
static void print(int a[], int n)
{
for (int i = 0; i < n; i++)
System.out.print(a[i] + " ");
System.out.println();
}
// Driver Code
public static void main(String[] args)
throws java.lang.Exception
{
// Given array
int[] arr = { 2, 3, -4, -1, 6, -9 };
int n = arr.length;
System.out.println("Given array is ");
print(arr, n);
int neg = 0, pos = 0;
for (int i = 0; i < n; i++) {
if (arr[i] < 0)
neg++;
else
pos++;
}
// Sort the array
Arrays.sort(arr);
if (neg <= pos) {
fill1(arr, neg, pos);
}
else {
// reverse the array in this condition
reverse(arr, n);
fill2(arr, neg, pos);
}
System.out.println("Rearranged array is ");
print(arr, n);
}
}Python3
# Python3 program for the above approach
# Function which works in the condition
# when number of negative numbers are
# lesser or equal than positive numbers
def fill1(a, neg, pos) :
if (neg % 2 == 1) :
for i in range(1, neg, 2):
c = a[i]
d = a[i + neg]
temp = c
a[i] = d
a[i + neg] = temp
else :
for i in range(1, neg+1, 2):
c = a[i]
d = a[i + neg - 1]
temp = c
a[i] = d
a[i + neg - 1] = temp
# Function which works in the condition
# when number of negative numbers are
# greater than positive numbers
def fill2(a, neg, pos):
if (pos % 2 == 1) :
for i in range(1, pos, 2):
c = a[i]
d = a[i + pos]
temp = c
a[i] = d
a[i + pos] = temp
else :
for i in range(1, pos+1, 2):
c = a[i]
d = a[i + pos - 1]
temp = c
a[i] = d
a[i + pos - 1] = temp
# Reverse the array
def reverse(a, n) :
for i in range(n / 2):
t = a[i]
a[i] = a[n - i - 1]
a[n - i - 1] = t
# Print the array
def printt(a, n):
for i in range(n):
print(a[i], end = " ")
print()
# Driver code
if __name__ == "__main__":
arr = [ 2, 3, -4, -1, 6, -9 ]
n = len(arr)
print("Given array is ")
printt(arr, n)
neg = 0
pos = 0
for i in range(0, n):
if (arr[i] < 0):
neg += 1
else:
pos += 1
# Sort the array
arr.sort()
if (neg <= pos) :
fill1(arr, neg, pos)
else :
# Reverse the array in this condition
reverse(arr, n)
fill2(arr, neg, pos)
print("Rearranged array is ")
printt(arr, n)
# This code is contributed by sanjoy_62.C#
// C# program for the above approach
using System;
using System.Collections.Generic;
using System.Linq;
public class GFG {
// function which works in the condition when number of
// negative numbers are lesser or equal than positive
// numbers
static void fill1(int[] a, int neg, int pos)
{
if (neg % 2 == 1) {
for (int i = 1; i < neg; i += 2) {
int c = a[i];
int d = a[i + neg];
int temp = c;
a[i] = d;
a[i + neg] = temp;
}
}
else {
for (int i = 1; i <= neg; i += 2) {
int c = a[i];
int d = a[i + neg - 1];
int temp = c;
a[i] = d;
a[i + neg - 1] = temp;
}
}
}
// Function which works in the condition when number of
// negative numbers are greater than positive numbers
static void fill2(int[] a, int neg, int pos)
{
if (pos % 2 == 1) {
for (int i = 1; i < pos; i += 2) {
int c = a[i];
int d = a[i + pos];
int temp = c;
a[i] = d;
a[i + pos] = temp;
}
}
else {
for (int i = 1; i <= pos; i += 2) {
int c = a[i];
int d = a[i + pos - 1];
int temp = c;
a[i] = d;
a[i + pos - 1] = temp;
}
}
}
// Reverse the array
static void reverse(int[] a, int n)
{
int i, k, t;
for (i = 0; i < n / 2; i++) {
t = a[i];
a[i] = a[n - i - 1];
a[n - i - 1] = t;
}
}
// Print the array
static void print(int[] a, int n)
{
for (int i = 0; i < n; i++)
Console.Write(a[i] + " ");
Console.WriteLine();
}
// Driver Code
public static void Main (string[] args) {
// Given array
int[] arr = { 2, 3, -4, -1, 6, -9 };
int n = arr.Length;
Console.WriteLine("Given array is ");
print(arr, n);
int neg = 0, pos = 0;
for (int i = 0; i < n; i++) {
if (arr[i] < 0)
neg++;
else
pos++;
}
// Sort the array
Array.Sort(arr);
if (neg <= pos) {
fill1(arr, neg, pos);
}
else {
// reverse the array in this condition
reverse(arr, n);
fill2(arr, neg, pos);
}
Console.WriteLine("Rearranged array is ");
print(arr, n);
}
}
// This code is contributed by splevel62.Javascript
C++
// C++ program to rearrange
// array in alternating
// positive & negative items
// with O(1) extra space
#include
using namespace std;
// Function to rearrange positive and negative
// integers in alternate fashion. The below
// solution doesn't maintain original order of
// elements
void rearrange(int arr[], int n)
{
int i = 0, j = n-1;
// shift all negative values to the end
while (i < j) {
while (i <= n - 1 and arr[i] > 0)
i += 1;
while (j >= 0 and arr[j] < 0)
j -= 1;
if (i < j )
swap(arr[i], arr[j]);
}
// i has index of leftmost
// negative element
if (i == 0 || i == n)
return;
// start with first positive
// element at index 0
// Rearrange array in alternating
// positive &
// negative items
int k = 0;
while (k < n && i < n ) {
// swap next positive
// element at even position
// from next negative element.
swap(arr[k], arr[i]);
i = i + 1;
k = k + 2;
}
}
// Utility function to print an array
void printArray(int arr[], int n)
{
for (int i = 0; i < n; i++)
cout << arr[i] << " ";
cout << endl;
}
// Driver code
int main()
{
int arr[] = { 2, 3, -4, -1, 6, -9 };
int n = sizeof(arr) / sizeof(arr[0]);
cout << "Given array is \n";
printArray(arr, n);
rearrange(arr, n);
cout << "Rearranged array is \n";
printArray(arr, n);
return 0;
} Java
// Java program to rearrange
// array in alternating
// positive & negative
// items with O(1) extra space
class GFG {
// Function to rearrange positive and negative
// integers in alternate fashion. The below
// solution doesn't maintain original order of
// elements
static void rearrange(int arr[], int n)
{
int i = 0, j = n - 1;
// shift all negative values to the end
while (i < j) {
while (i <= n - 1 && arr[i] > 0)
i += 1;
while (j >= 0 && arr[j] < 0)
j -= 1;
if (i < j)
swap(arr, i, j);
}
// i has index of leftmost negative element
if (i == 0 || i == n)
return;
// start with first positive
// element at index 0
// Rearrange array in alternating positive &
// negative items
int k = 0;
while (k < n && i < n) {
// swap next positive element
// at even position
// from next negative element.
swap(arr, k, i);
i = i + 1;
k = k + 2;
}
}
// Utility function to print an array
static void printArray(int arr[], int n)
{
for (int i = 0; i < n; i++)
System.out.print(arr[i] + " ");
System.out.println("");
}
static void swap(int arr[], int index1, int index2)
{
int c = arr[index1];
arr[index1] = arr[index2];
arr[index2] = c;
}
// Driver code
public static void main(String[] args)
{
int arr[] = { 2, 3, -4, -1, 6, -9 };
int n = arr.length;
System.out.println("Given array is ");
printArray(arr, n);
rearrange(arr, n);
System.out.println("Rearranged array is ");
printArray(arr, n);
}
}
// This code is contributed by 29AjayKumarPython3
# Python3 program to rearrange array
# in alternating positive & negative
# items with O(1) extra space
# Function to rearrange positive and
# negative integers in alternate fashion.
# The below solution does not maintain
# original order of elements
def rearrange(arr, n):
i = 0
j = n - 1
# shift all negative values
# to the end
while (i < j):
while (i <= n - 1 and arr[i] > 0):
i += 1
while (j >= 0 and arr[j] < 0):
j -= 1
if (i < j):
temp = arr[i]
arr[i] = arr[j]
arr[j] = temp
# i has index of leftmost
# negative element
if (i == 0 or i == n):
return 0
# start with first positive element
# at index 0
# Rearrange array in alternating
# positive & negative items
k = 0
while (k < n and i < n):
# swap next positive element at even
# position from next negative element.
temp = arr[k]
arr[k] = arr[i]
arr[i] = temp
i = i + 1
k = k + 2
# Utility function to print an array
def printArray(arr, n):
for i in range(n):
print(arr[i], end=" ")
print("\n")
# Driver code
arr = [2, 3]
n = len(arr)
print("Given array is")
printArray(arr, n)
rearrange(arr, n)
print("Rearranged array is")
printArray(arr, n)
# This code is contributed
# Princi SinghC#
// C# program to rearrange array
// in alternating positive & negative
// items with O(1) extra space
using System;
class GFG {
// Function to rearrange positive and
// negative integers in alternate fashion.
// The below solution doesn't maintain
// original order of elements
static void rearrange(int[] arr, int n)
{
int i = 0, j = n - 1;
// shift all negative values
// to the end
while (i < j) {
while (i <= n - 1 && arr[i] > 0)
i += 1;
while (j >= 0 && arr[j] < 0)
j -= 1;
if (i < j)
swap(arr, i, j);
}
// i has index of leftmost
// negative element
if (i == 0 || i == n)
return;
// start with first positive
// element at index 0
// Rearrange array in alternating
// positive & negative items
int k = 0;
while (k < n && i < n) {
// swap next positive element
// at even position from next
// negative element.
swap(arr, k, i);
i = i + 1;
k = k + 2;
}
}
// Utility function to print an array
static void printArray(int[] arr, int n)
{
for (int i = 0; i < n; i++)
Console.Write(arr[i] + " ");
Console.WriteLine("");
}
static void swap(int[] arr, int index1, int index2)
{
int c = arr[index1];
arr[index1] = arr[index2];
arr[index2] = c;
}
// Driver code
public static void Main()
{
int[] arr = { 2, 3, -4, -1, 6, -9 };
int n = arr.Length;
Console.WriteLine("Given array is ");
printArray(arr, n);
rearrange(arr, n);
Console.WriteLine("Rearranged array is ");
printArray(arr, n);
}
}
// This code is contributed
// by 29AjayKumarPHP
0)
++$i;
while ($j >= 0 and $arr[$j] < 0)
--$j;
if ($i < $j)
{
$temp = $arr[$i];
$arr[$i] = $arr[$j];
$arr[$j] = $temp;
}
}
// i has index of leftmost
// negative element
if ($i == 0 || $i == $n)
return;
// start with first positive element
// at index 0
// Rearrange array in alternating
// positive & negative items
$k = 0;
while ($k < $n && $i < $n)
{
// swap next positive element at even
// position from next negative element.
$temp = $arr[$k];
$arr[$k] = $arr[$i];
$arr[$i] = $temp;
$i = $i + 1;
$k = $k + 2;
}
}
// Utility function to print an array
function printArray(&$arr, $n)
{
for ($i = 0; $i < $n; $i++)
echo $arr[$i] . " ";
echo "\n";
}
// Driver code
$arr = array(2, 3, -4, -1, 6, -9);
$n = sizeof($arr);
echo "Given array is \n";
printArray($arr, $n);
rearrange($arr, $n);
echo "Rearranged array is \n";
printArray($arr, $n);
// This code is contributed
// by ChitraNayal
?>Javascript
输出
Given array is
2 3 -4 -1 6 -9
Rearranged array is
-9 3 -1 2 -4 6时间复杂度： O(N*logN)
空间复杂度： O(1)
有效的方法：
我们已经讨论了一个 O(n 2 ) 解决方案，它在这里保持数组中出现的顺序。如果允许我们改变出现的顺序，我们可以在 O(n) 时间和 O(1) 空间内解决这个问题。
这个想法是处理数组并在 O(n) 时间内将所有负值移到末尾。在所有负值都移到末尾之后，我们可以轻松地在交替的正负项中重新排列数组。在这一步中，我们基本上从下一个负元素交换偶数位置的下一个正元素。
以下是上述思想的实现。
C++
// C++ program to rearrange
// array in alternating
// positive & negative items
// with O(1) extra space
#include
using namespace std;
// Function to rearrange positive and negative
// integers in alternate fashion. The below
// solution doesn't maintain original order of
// elements
void rearrange(int arr[], int n)
{
int i = 0, j = n-1;
// shift all negative values to the end
while (i < j) {
while (i <= n - 1 and arr[i] > 0)
i += 1;
while (j >= 0 and arr[j] < 0)
j -= 1;
if (i < j )
swap(arr[i], arr[j]);
}
// i has index of leftmost
// negative element
if (i == 0 || i == n)
return;
// start with first positive
// element at index 0
// Rearrange array in alternating
// positive &
// negative items
int k = 0;
while (k < n && i < n ) {
// swap next positive
// element at even position
// from next negative element.
swap(arr[k], arr[i]);
i = i + 1;
k = k + 2;
}
}
// Utility function to print an array
void printArray(int arr[], int n)
{
for (int i = 0; i < n; i++)
cout << arr[i] << " ";
cout << endl;
}
// Driver code
int main()
{
int arr[] = { 2, 3, -4, -1, 6, -9 };
int n = sizeof(arr) / sizeof(arr[0]);
cout << "Given array is \n";
printArray(arr, n);
rearrange(arr, n);
cout << "Rearranged array is \n";
printArray(arr, n);
return 0;
}
Java
// Java program to rearrange
// array in alternating
// positive & negative
// items with O(1) extra space
class GFG {
// Function to rearrange positive and negative
// integers in alternate fashion. The below
// solution doesn't maintain original order of
// elements
static void rearrange(int arr[], int n)
{
int i = 0, j = n - 1;
// shift all negative values to the end
while (i < j) {
while (i <= n - 1 && arr[i] > 0)
i += 1;
while (j >= 0 && arr[j] < 0)
j -= 1;
if (i < j)
swap(arr, i, j);
}
// i has index of leftmost negative element
if (i == 0 || i == n)
return;
// start with first positive
// element at index 0
// Rearrange array in alternating positive &
// negative items
int k = 0;
while (k < n && i < n) {
// swap next positive element
// at even position
// from next negative element.
swap(arr, k, i);
i = i + 1;
k = k + 2;
}
}
// Utility function to print an array
static void printArray(int arr[], int n)
{
for (int i = 0; i < n; i++)
System.out.print(arr[i] + " ");
System.out.println("");
}
static void swap(int arr[], int index1, int index2)
{
int c = arr[index1];
arr[index1] = arr[index2];
arr[index2] = c;
}
// Driver code
public static void main(String[] args)
{
int arr[] = { 2, 3, -4, -1, 6, -9 };
int n = arr.length;
System.out.println("Given array is ");
printArray(arr, n);
rearrange(arr, n);
System.out.println("Rearranged array is ");
printArray(arr, n);
}
}
// This code is contributed by 29AjayKumar
Python3
# Python3 program to rearrange array
# in alternating positive & negative
# items with O(1) extra space
# Function to rearrange positive and
# negative integers in alternate fashion.
# The below solution does not maintain
# original order of elements
def rearrange(arr, n):
i = 0
j = n - 1
# shift all negative values
# to the end
while (i < j):
while (i <= n - 1 and arr[i] > 0):
i += 1
while (j >= 0 and arr[j] < 0):
j -= 1
if (i < j):
temp = arr[i]
arr[i] = arr[j]
arr[j] = temp
# i has index of leftmost
# negative element
if (i == 0 or i == n):
return 0
# start with first positive element
# at index 0
# Rearrange array in alternating
# positive & negative items
k = 0
while (k < n and i < n):
# swap next positive element at even
# position from next negative element.
temp = arr[k]
arr[k] = arr[i]
arr[i] = temp
i = i + 1
k = k + 2
# Utility function to print an array
def printArray(arr, n):
for i in range(n):
print(arr[i], end=" ")
print("\n")
# Driver code
arr = [2, 3]
n = len(arr)
print("Given array is")
printArray(arr, n)
rearrange(arr, n)
print("Rearranged array is")
printArray(arr, n)
# This code is contributed
# Princi Singh
C＃
// C# program to rearrange array
// in alternating positive & negative
// items with O(1) extra space
using System;
class GFG {
// Function to rearrange positive and
// negative integers in alternate fashion.
// The below solution doesn't maintain
// original order of elements
static void rearrange(int[] arr, int n)
{
int i = 0, j = n - 1;
// shift all negative values
// to the end
while (i < j) {
while (i <= n - 1 && arr[i] > 0)
i += 1;
while (j >= 0 && arr[j] < 0)
j -= 1;
if (i < j)
swap(arr, i, j);
}
// i has index of leftmost
// negative element
if (i == 0 || i == n)
return;
// start with first positive
// element at index 0
// Rearrange array in alternating
// positive & negative items
int k = 0;
while (k < n && i < n) {
// swap next positive element
// at even position from next
// negative element.
swap(arr, k, i);
i = i + 1;
k = k + 2;
}
}
// Utility function to print an array
static void printArray(int[] arr, int n)
{
for (int i = 0; i < n; i++)
Console.Write(arr[i] + " ");
Console.WriteLine("");
}
static void swap(int[] arr, int index1, int index2)
{
int c = arr[index1];
arr[index1] = arr[index2];
arr[index2] = c;
}
// Driver code
public static void Main()
{
int[] arr = { 2, 3, -4, -1, 6, -9 };
int n = arr.Length;
Console.WriteLine("Given array is ");
printArray(arr, n);
rearrange(arr, n);
Console.WriteLine("Rearranged array is ");
printArray(arr, n);
}
}
// This code is contributed
// by 29AjayKumar
PHP
0)
++$i;
while ($j >= 0 and $arr[$j] < 0)
--$j;
if ($i < $j)
{
$temp = $arr[$i];
$arr[$i] = $arr[$j];
$arr[$j] = $temp;
}
}
// i has index of leftmost
// negative element
if ($i == 0 || $i == $n)
return;
// start with first positive element
// at index 0
// Rearrange array in alternating
// positive & negative items
$k = 0;
while ($k < $n && $i < $n)
{
// swap next positive element at even
// position from next negative element.
$temp = $arr[$k];
$arr[$k] = $arr[$i];
$arr[$i] = $temp;
$i = $i + 1;
$k = $k + 2;
}
}
// Utility function to print an array
function printArray(&$arr, $n)
{
for ($i = 0; $i < $n; $i++)
echo $arr[$i] . " ";
echo "\n";
}
// Driver code
$arr = array(2, 3, -4, -1, 6, -9);
$n = sizeof($arr);
echo "Given array is \n";
printArray($arr, $n);
rearrange($arr, $n);
echo "Rearranged array is \n";
printArray($arr, $n);
// This code is contributed
// by ChitraNayal
?>
Javascript
输出：
Given array is
2 3 -4 -1 6 -9
Rearranged array is
-1 3 -4 2 -9 6时间复杂度： O(N)
空间复杂度： O(1)