题目地址

Given N integers, you are supposed to find the smallest positive integer that is NOT in the given list.

Input Specification:
Each input file contains one test case. For each case, the first line gives a positive integer N (≤10
​5
​​ ). Then N integers are given in the next line, separated by spaces. All the numbers are in the range of int.

Output Specification:
Print in a line the smallest positive integer that is missing from the input list.

Sample Input:
10
5 -25 9 6 1 3 4 2 5 17

Sample Output:
7

#include <cstdio>
#include <cstring>
#include<iostream>
#include <vector>
#include<math.h>
#include<string>
#include<queue>
#include <algorithm>
#include<set>
#include<map>
using namespace std;
const int maxn=100010,inf=1000000;
int n,a[maxn],low=inf;
map<int,bool>exsit;
int main(){
    cin>>n;
    for(int i=0;i<n;i++) {
        cin>>a[i];
        low=min(a[i],low);exsit[a[i]]=1;
    }
    // if(low==inf){
    //     cout<<"1"<<endl;return 0;
    // }
    int i;
    for(i=max(low,1);;i++){
        if(!exsit[i]){
            cout<<i<<endl;break;
        }
    }
    return 0;
}