PAT (Advanced Level) Practice — 1144 The Missing Number （20 分）

原创于 2019-02-27 08:50:38 发布 · 147 阅读

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本文介绍了一种算法，用于从给定的整数列表中找出最小的未出现的正整数。通过读取输入的整数列表，使用布尔数组标记已存在的正整数，并遍历查找第一个未被标记的位置，从而高效地找到缺失的正整数。

题目链接：https://pintia.cn/problem-sets/994805342720868352/problems/994805343463260160

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:

：注意 如果不加最大范围的判断提交会产生段错误。

#include<iostream>
#include<cstring>
using namespace std;
int main(){
	int n;
	cin>>n;
	int a;
	bool f[100010];
	memset(f,0,sizeof(f));
	for(int i=0;i<n;i++){
		cin>>a;
		if(a<=0||a>100010){
			continue;
		}
		f[a]=1;
	}
	for(int i=1;;i++){
		if(f[i]==0){
			cout<<i<<endl;
			break;
		}
	}
	return 0;
}