PAT_A1144#The Missing Number

Source:

PAT A1144 The Missing Number (20 分)

Description:

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

Keys:

• 散列（Hash）

Code:

/*
Data: 2019-05-23 19:50:36
Problem: PAT_A1144#The Missing Number
AC: 05:24

题目大意：
给定N（<=1e5）个整数（int范围内），找出不在表中的最小正数；
*/

#include<cstdio>
#include<map>

int main()
{
#ifdef    ONLINE_JUDGE
#else
    freopen("Test.txt", "r", stdin);
#endif

    int n,x;
    std::map<int,int> mp;
    scanf("%d", &n);
    for(int i=0; i<n; i++)
    {
        scanf("%d", &x);
        mp[x]=1;
    }
    for(int i=1; i<1e9; i++)
    {
        if(mp[i]==0)
        {
            printf("%d\n", i);
            break;
        }
    }


    return 0;
}