Luogu P3370 【模板】字符串哈希

gate

对于每一位(s[i])
(ans = (ans*base + (ull)s[i])\%mod + prime)

建议数值
(base = 131\ prime = 233317\ mod1 = 19260817\ mod2 = 20031101)

• 双哈希

#include<cstdio>
#include<iostream>
#include<cmath>
#include<cstring>
#include<algorithm>
#define MogeKo qwq
#define ull unsigned long long
using namespace std;

ull base = 131;
struct node {
	ull x,y;
	bool operator < (const node &N)const {
		return x<N.x || ((x==N.x) && (y<N.y));
	}
} a[10010];
char s[10010];

int n,ans;
int prime = 233317;
ull mod1 = 19260817;
ull mod2 = 20031101;

ull hash1(char s[]) {
	int len = strlen(s);
	ull ans = 0;
	for(int i = 0; i < len; i++)
		ans = (ans*base + (ull)s[i])%mod1 + prime;
	return ans;
}

ull hash2(char s[]) {
	int len = strlen(s);
	ull ans = 0;
	for(int i = 0; i < len; i++)
		ans = (ans*base + (ull)s[i])%mod2 + prime;
	return ans;
}

int main() {
	scanf("%d",&n);
	for (int i = 1; i <= n; i++) {
		scanf("%s",s);
		a[i].x = hash1(s);
		a[i].y = hash2(s);
	}
	sort(a+1,a+n+1);
	ans = 1;
	for(int i = 1; i < n; i++) {
		if(a[i].x != a[i+1].x || a[i].y != a[i+1].y)
			ans++;
	}
	printf("%d
",ans);
	return 0;
}

• 单哈希

#include<cstdio>
#include<iostream>
#include<cmath>
#include<cstring>
#include<algorithm>
#define MogeKo qwq
#define ull unsigned long long
using namespace std;

ull base = 131;
ull a[10010];
char s[10010];
int n,ans;
int prime = 233317;
ull mod = 212370440130137957ll;

ull hashi(char s[]){
	int len = strlen(s);
	ull ans = 0;
	for(int i = 0;i < len;i++)
		ans = (ans*base + (ull)s[i])%mod + prime;
	return ans;
}

int main() {
	scanf("%d",&n);
	for(int i = 1; i <= n; i++) {
		scanf("%s",s);
		a[i] = hashi(s);
	}
	sort(a+1,a+n+1);
	ans = 1;
	for(int i = 1; i < n; i++) {
		if(a[i] != a[i+1])
			ans++;
	}
	printf("%d",ans);
}