PAT-A 真题 – 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 (≤105). 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

题目大意：给定n的数字，求出最小的没有出现的正整数。

这道题记录所有的正整数，然后排序即可。但是要注意给定数字可能有重复的！

这道题使用set再合适不过了，自动排序，去重，美滋滋~

代码：

#include <iostream>
#include <set>
using namespace std;

int main(){
  int cnt;
  cin >> cnt;
  set<int> input;
  for(int i = 0; i < cnt; i++){
    int tmp;
    cin >> tmp;
    if(tmp > 0) input.insert(tmp);
  }
  int num = 1;
  for(set<int>::iterator it = input.begin(); it != input.end(); it++){
    if(num != *it)
      break;
    num++;
  }
  cout << num;
  return 0;
}