给定一个未排序的数组，其中同时包含正和负元素。任务是找到数组中缺少的最小正数。
例子：
Input: arr[] = {2, 3, 7, 6, 8, -1, -10, 15}
Output: 1
Input: arr[] = { 2, 3, -7, 6, 8, 1, -10, 15 }
Output: 4
Input: arr[] = {1, 1, 0, -1, -2}
Output: 2
方法 ：
我们已经讨论了一些从未排序的数组中寻找最小正数的技术。
查找未排序数组中缺失的最小正数|套装1
查找未排序数组中缺失的最小正数|套装2
在这里，我们使用set存储所有正整数，并找到第一个缺失的正整数。
C++
// CPP program to find the smallest
// positive missing number
#include
using namespace std;
// Function to find the smallest
// positive missing number
int findMissingPositive(int arr[], int n)
{
// Default smallest Positive Integer
int m = 1;
// Store values in set which are
// greater than variable m
set x;
for (int i = 0; i < n; i++) {
// Store value when m is less than
// current index of given array
if (m < arr[i]) {
x.insert(arr[i]);
}
else if (m == arr[i]) {
// Increment m when it is equal
// to current element
m = m + 1;
while (x.count(m)) {
x.erase(m);
// Increment m when it is one of the
// element of the set
m = m + 1;
}
}
}
// Return the required answer
return m;
}
// Driver code
int main()
{
int arr[] = { 2, 3, -7, 6, 8, 1, -10, 15 };
int n = sizeof(arr) / sizeof(arr[0]);
// Function call
cout << findMissingPositive(arr, n);
return 0;
} Java
// Java program to find the smallest
// positive missing number
import java.util.*;
class GFG
{
// Function to find the smallest
// positive missing number
static int findMissingPositive(int arr[], int n)
{
// Default smallest Positive Integer
int m = 1;
// Store values in set which are
// greater than variable m
HashSet x = new HashSet();
for (int i = 0; i < n; i++)
{
// Store value when m is less than
// current index of given array
if (m < arr[i])
{
x.add(arr[i]);
}
else if (m == arr[i])
{
// Increment m when it is equal
// to current element
m = m + 1;
while (x.contains(m))
{
x.remove(m);
// Increment m when it is one of the
// element of the set
m = m + 1;
}
}
}
// Return the required answer
return m;
}
// Driver code
public static void main(String[] args)
{
int arr[] = { 2, 3, -7, 6, 8, 1, -10, 15 };
int n = arr.length;
// Function call
System.out.println(findMissingPositive(arr, n));
}
}
// This code is contributed by 29AjayKumar Python3
# Python 3 program to find the smallest
# positive missing number
# Function to find the smallest
# positive missing number
def findMissingPositive(arr, n):
# Default smallest Positive Integer
m = 1
# Store values in set which are
# greater than variable m
x = []
for i in range(n):
# Store value when m is less than
# current index of given array
if (m < arr[i]):
x.append(arr[i])
elif (m == arr[i]):
# Increment m when it is equal
# to current element
m = m + 1
while (x.count(m)):
x.remove(m)
# Increment m when it is one of the
# element of the set
m = m + 1
# Return the required answer
return m
# Driver code
if __name__ == '__main__':
arr = [2, 3, -7, 6, 8, 1, -10, 15]
n = len(arr)
# Function call
print(findMissingPositive(arr, n))
# This code is contributed by
# Surendra_GangwarC#
// C# program to find the smallest
// positive missing number
using System;
using System.Collections.Generic;
class GFG
{
// Function to find the smallest
// positive missing number
static int findMissingPositive(int []arr, int n)
{
// Default smallest Positive Integer
int m = 1;
// Store values in set which are
// greater than variable m
HashSet x = new HashSet();
for (int i = 0; i < n; i++)
{
// Store value when m is less than
// current index of given array
if (m < arr[i])
{
x.Add(arr[i]);
}
else if (m == arr[i])
{
// Increment m when it is equal
// to current element
m = m + 1;
while (x.Contains(m))
{
x.Remove(m);
// Increment m when it is one of the
// element of the set
m = m + 1;
}
}
}
// Return the required answer
return m;
}
// Driver code
public static void Main(String[] args)
{
int []arr = { 2, 3, -7, 6, 8, 1, -10, 15 };
int n = arr.Length;
// Function call
Console.WriteLine(findMissingPositive(arr, n));
}
}
// This code is contributed by Rajput-Ji 输出：
4