1144 The Missing Number

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 (≤). 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

注意点：考虑两种极端情况； 1.所有数都小于零 2.所有数都大于1

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
int main(){
  int n, i;
  cin>>n;
  vector<int> v(n);
  for(i=0; i<n; i++) cin>>v[i];
  sort(v.begin(), v.end());
  if(v[0]>1)cout<<v[0]-1<<endl;
  if(v[n-1]<0)cout<<1<<endl; 
  else{
    for(i=0; i<n; i++) if(v[i]>=0) break;
  bool flag=true;
  for(; i<n-1; i++){
    if(v[i+1]-v[i]>1){
      cout<<v[i]+1<<endl;
      flag=false;
      break;
    }
  }
  if(flag) cout<<v[n-1]+1<<endl;
  }
  return 0;
}