给定两个相同大小的未排序数组，编写一个函数，如果两个数组彼此置换，则返回true，否则返回false。
例子：
Input: arr1[] = {2, 1, 3, 5, 4, 3, 2}
arr2[] = {3, 2, 2, 4, 5, 3, 1}
Output: Yes
Input: arr1[] = {2, 1, 3, 5,}
arr2[] = {3, 2, 2, 4}
Output: No强烈建议您最小化浏览器，然后自己尝试。
一个简单的解决方案是对两个数组都进行排序并比较排序后的数组。该解决方案的时间复杂度为O(nLogn)
更好的解决方案是使用哈希。
- 为arr1 []的所有元素创建一个哈希映射，以使数组元素为键，其计数为值。
- 遍历arr2 []并在哈希图中搜索arr2 []的每个元素。如果找到一个元素，则减少其在哈希图中的计数。如果找不到，则返回false。
- 如果找到所有元素，则返回true。
以下是此方法的实现。
C++
// A C++ program to find one array is permutation of other array
#include
using namespace std;
// Returns true if arr1[] and arr2[] are permutations of each other
bool arePermutations(int arr1[], int arr2[], int n, int m)
{
// Arrays cannot be permutations of one another unless they are
// of the same length
if(n != m)
{
return false;
}
// Creates an empty hashMap hM
map hm;
// Traverse through the first array and add elements to hash map
for (int i = 0; i < n; i++)
{
int x = arr1[i];
hm[x]++;
}
// Traverse through second array and check if every element is
// present in hash map
for (int i = 0; i < m; i++)
{
int x = arr2[i];
// If element is not present in hash map or element
// is not present less number of times
if(hm[x] == 0)
{
return false;
}
hm[x]--;
}
return true;
}
// Driver function to test above function
int main() {
int arr1[] = {2, 1, 3, 5, 4, 3, 2};
int arr2[] = {3, 2, 2, 4, 5, 3, 1};
int n = sizeof(arr1)/sizeof(arr1[0]);
int m = sizeof(arr2)/sizeof(arr2[0]);
if (arePermutations(arr1, arr2, n, m))
cout << "Arrays are permutations of each other" << endl;
else
cout << "Arrays are NOT permutations of each other" << endl;
return 0;
}
// This code is contributed by avanitrachhadiya2155 Java
// A Java program to find one array is permutation of other array
import java.util.HashMap;
class Permutaions
{
// Returns true if arr1[] and arr2[] are permutations of each other
static Boolean arePermutations(int arr1[], int arr2[])
{
// Arrays cannot be permutations of one another unless they are
// of the same length
if (arr1.length != arr2.length)
return false;
// Creates an empty hashMap hM
HashMap hM = new HashMap();
// Traverse through the first array and add elements to hash map
for (int i = 0; i < arr1.length; i++)
{
int x = arr1[i];
if (hM.get(x) == null)
hM.put(x, 1);
else
{
int k = hM.get(x);
hM.put(x, k+1);
}
}
// Traverse through second array and check if every element is
// present in hash map
for (int i = 0; i < arr2.length; i++)
{
int x = arr2[i];
// If element is not present in hash map or element
// is not present less number of times
if (hM.get(x) == null || hM.get(x) == 0)
return false;
int k = hM.get(x);
hM.put(x, k-1);
}
return true;
}
// Driver function to test above function
public static void main(String arg[])
{
int arr1[] = {2, 1, 3, 5, 4, 3, 2};
int arr2[] = {3, 2, 2, 4, 5, 3, 1};
if (arePermutations(arr1, arr2))
System.out.println("Arrays are permutations of each other");
else
System.out.println("Arrays are NOT permutations of each other");
}
} Python3
# Python3 program to find one
# array is permutation of other array
from collections import defaultdict
# Returns true if arr1[] and
# arr2[] are permutations of
# each other
def arePermutations(arr1, arr2):
# Arrays cannot be permutations of one another
# unless they are of the same length
if (len(arr1) != len(arr2)):
return False
# Creates an empty hashMap hM
hM = defaultdict (int)
# Traverse through the first
# array and add elements to
# hash map
for i in range (len(arr1)):
x = arr1[i]
hM[x] += 1
# Traverse through second array
# and check if every element is
# present in hash map
for i in range (len(arr2)):
x = arr2[i]
# If element is not present
# in hash map or element
# is not present less number
# of times
if x not in hM or hM[x] == 0:
return False
hM[x] -= 1
return True
# Driver code
if __name__ == "__main__":
arr1 = [2, 1, 3, 5, 4, 3, 2]
arr2 = [3, 2, 2, 4, 5, 3, 1]
if (arePermutations(arr1, arr2)):
print("Arrays are permutations of each other")
else:
print("Arrays are NOT permutations of each other")
# This code is contributed by ChitranayalC#
// C# program to find one array
// is permutation of other array
using System;
using System.Collections.Generic;
public class Permutaions {
// Returns true if arr1[] and arr2[]
// are permutations of each other
static Boolean arePermutations(int[] arr1, int[] arr2)
{
// Arrays cannot be permutations of one another if
// they are not the the same length
if (arr1.Length != arr2.Length)
return false;
// Creates an empty hashMap hM
Dictionary hM = new Dictionary();
// Traverse through the first array
// and add elements to hash map
for (int i = 0; i < arr1.Length; i++) {
int x = arr1[i];
if (!hM.ContainsKey(x))
hM.Add(x, 1);
else {
int k = hM[x];
hM.Remove(x);
hM.Add(x, k + 1);
}
}
// Traverse through second array and check if every
// element is present in hash map (and the same
// number of times)
for (int i = 0; i < arr2.Length; i++) {
int x = arr2[i];
// If element is not present in hash map or
// element is not present the same number of
// times
if (!hM.ContainsKey(x))
return false; // Not present in the hash map
int k = hM[x];
if (k == 0)
return false; // Not present the same number
// of times
hM.Remove(x);
hM.Add(x, k - 1);
}
return true;
}
// Driver code
public static void Main()
{
int[] arr1 = { 2, 1, 3, 5, 4, 3, 2 };
int[] arr2 = { 3, 2, 2, 4, 5, 3, 1 };
if (arePermutations(arr1, arr2))
Console.WriteLine("Arrays are permutations of each other");
else
Console.WriteLine("Arrays are NOT permutations of each other");
}
}
/* This code contributed by PrinciRaj1992 */ 输出
Arrays are permutations of each other