1. 程式人生 > >PAT (Advanced Level) 1078 Hashing (雜湊、平方探測衝突處理Quadratic probing)

PAT (Advanced Level) 1078 Hashing (雜湊、平方探測衝突處理Quadratic probing)

 記錄下這題是因為注意平方探測的公式是:position = (key + index^{i}) % TableSize;\textbf{mod} TableSize,其中i = 0,1,2...TableSize

而非先對key取模再加平方。

這題質數範圍不大,不用二分直接掃也不會T。

#include<bits/stdc++.h>
using namespace std;


int m,n;
int cnt;
int prime[1300];
void init(){
	cnt = 0;
	for(int i = 2; i <= 10007; ++i){
		int flag = 1;
		for(int j = 2; j <= sqrt(i); ++j){
			if(i % j == 0){flag = 0; break;}
		}
		if(flag) prime[++cnt] = i;
	}
}
void findp(int *p){
	int l = 1, r = cnt, mid;
	while(l <= r){
		mid = (l + r) / 2;
		if(prime[mid] == *p) break;
		if(prime[mid] > *p) r = mid - 1;
		else l = mid + 1;
	}
	if(*p > prime[mid]) *p = prime[mid+1];
	else *p = prime[mid];
}
int ht[10010];
int res[10010];
int hashx(int x){
	int add = x % m, index = 1;
	while(index < m){
		if(ht[add] == -1){
			ht[add] = x;
			return add;
		}
		else{
			add = (x + index * index) % m;
			++index;
		}
	}
	return -1;
}

int main(){
	init();
	scanf("%d%d",&m,&n);
	findp(&m);
	int x;
	memset(ht,-1,sizeof(ht));
	for(int i = 0; i < n; ++i){
		scanf("%d",&x);
		res[i] = hashx(x);
	}
	printf("%d",res[0]);
	for(int i = 1; i < n; ++i){
		if(res[i] != -1)
			printf(" %d",res[i]);
		else 
			printf(" -");
	}
	return 0;
}