题解 | #Prime Number#

//土尔逊Torson 编写于2023/05/09
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <cstdio>
#include <vector>

using namespace std;

const int MAXN = 100001;

vector<int>prime07101;       //保存质数
bool isPrime07101[MAXN];     //标记数组

void Initial07101() {
	for (int i = 0; i < MAXN; ++i) {   //初始化
		isPrime07101[i] = true;
	}
	isPrime07101[0] = false;
	isPrime07101[1] = false;
	for (int i = 2; i < MAXN; ++i) {
		if (!isPrime07101[i]) {             //非质数则跳过
			continue;
		}
		prime07101.push_back(i);
		for (int j = i*i; j < MAXN; j += i) {
			isPrime07101[j] = false;        //质数的倍数为非质数
		}
	}
	return;
}

int main() {
	Initial07101();
	int n;
	while (scanf("%d", &n) != EOF) {
		int count = 0;
		int pos = 0;
		for (int i = 0; i < prime07101.size() && count < n; ++i) {
			if (prime07101[i]) { //记录第 N 个 Prime
				count++;
				pos = i;
			}
		}
		printf("%d\n", prime07101[pos]); //输出第 N 个 Prime
	}
	system("pause");
	return EXIT_SUCCESS;
}
// 64 位输出请用 printf("%lld")