PAT 1144. The Missing Number (20) – 甲级

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

分析:将每个数字出现的次数存储在map里面,num从1开始,如果m[num] == 0说明不存在,则输出这个num~