PAT甲级 1078 Hashing

原题链接：

https://pintia.cn/problem-sets/994805342720868352/exam/problems/type/7?problemSetProblemId=994805389634158592&page=0

注意点：

1. Quadratic probing (with positive increments only) 平方探测的概念理解。

代码：

#include <iostream>
#include <vector>
using namespace std;

#define endl '\n'

const int maxM = 1e5;
int M, N, T;
int nums[maxM];
int pos[maxM];
vector<int> ans;

vector<int> isPrime(maxM,1);
int findT(int x) {
	//制作素数表
	isPrime[0] = 0;
	isPrime[1] = 0;
	for (int i = 2; i < maxM; i++) {
		for (int j = 2; i * j < maxM; j++) {
			isPrime[i * j] = 0;
		}
	}

	while (!isPrime[x]) {
		x++;
	}

	return x;
	
}

int quadraticProbe(int x) {//x%T被占据，进行平方探测法
	int start = x % T;
	for (int i = 0; i<T; i++) {
		int possiblePos = (start + i * i) % T;
		if (pos[possiblePos] == 0) {//找到了
			pos[possiblePos] = x;
			return possiblePos;
		}
	}
	return -1;
}

signed main() {
	ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);

	cin >> M >> N;
	T=findT(M);
	//cout << "T:" << T << endl;
	for (int i = 0; i < N; i++) {
		cin >> nums[i];
		ans.push_back(quadraticProbe(nums[i]));
	}

	for (int i = 0; i < ans.size(); i++) {
		if (ans[i] >= 0) {
			cout << ans[i];
		}
		else {
			cout << "-";
		}
		if (i != ans.size() - 1) {
			cout << " ";
		}
	}

	return 0;
}