1144 The Missing Number（20 分）
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
题意：给出n个数，输出不在给出的数中的最小正整数。
分析：1.用set去接收这些数（排序+去重）
题解：
#include<cstdlib>
#include<cstdio>
#include<set>
using namespace std;
int main() {
int n;
set<int> s;
scanf("%d", &n);
for (int i = 0; i != n; i++) {
int t;
scanf("%d", &t);
s.insert(t);
}
int pre = *(s.begin());
for (set<int>::iterator it = ++s.begin(); it != s.end(); it++) {
if (*it - pre != 1 && pre+1 > 0) {
printf("%d", pre + 1);
return 0;
}
pre = *(it);
}
//如果遍历到最后一个仍然找不到符合要求的结果，
//则输出最大的数之后的正整数（最大的数可能为正，或者仍为负）
if (pre >= 0) {
printf("%d", pre + 1);
}
else {
printf("%d", 1);
}
return 0;
}
