1144 The Missing Number

Posted 2020-11-18 mr-stn

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

 1 #include<iostream>
 2 #include<vector>
 3 #include<algorithm>
 4 using namespace std;
 5 int main(){
 6   int n, i;
 7   cin>>n;
 8   vector<int> v(n);
 9   for(i=0; i<n; i++) cin>>v[i];
10   sort(v.begin(), v.end());
11   if(v[0]>1)cout<<v[0]-1<<endl;
12   if(v[n-1]<0)cout<<1<<endl; 
13   else{
14     for(i=0; i<n; i++) if(v[i]>=0) break;
15   bool flag=true;
16   for(; i<n-1; i++){
17     if(v[i+1]-v[i]>1){
18       cout<<v[i]+1<<endl;
19       flag=false;
20       break;
21     }
22   }
23   if(flag) cout<<v[n-1]+1<<endl;
24   }
25   return 0;
26 }