【字符串哈希】 HDOJ 4080 Stammering Aliens

这道题用字符串哈希较慢。。。。C++超时。。。G++AC。。。

#include <iostream>  
#include <queue>  
#include <stack>  
#include <map>  
#include <set>  
#include <bitset>  
#include <cstdio>  
#include <algorithm>  
#include <cstring>  
#include <climits>
#include <cstdlib>
#include <cmath>
#include <time.h>
#define maxn 100000
#define maxm 40005
//#define eps 1e-10
#define mod 10000007
#define INF 1e9
#define lowbit(x) (x&(-x))
#define mp make_pair
#define ls o<<1
#define rs o<<1 | 1
#define lson o<<1, L, mid  
#define rson o<<1 | 1, mid+1, R  
typedef long long LL;
typedef unsigned long long ULL;
//typedef int LL;
using namespace std;
LL qpow(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base;base=base*base;b/=2;}return res;}
LL powmod(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base%mod;base=base*base%mod;b/=2;}return res;}
void scanf(int &__x){__x=0;char __ch=getchar();while(__ch==' '||__ch=='\n')__ch=getchar();while(__ch>='0'&&__ch<='9')__x=__x*10+__ch-'0',__ch = getchar();}
LL gcd(LL _a, LL _b){if(!_b) return _a;else return gcd(_b, _a%_b);}
//head

const int x = 123;
ULL hash[maxn], xp[maxn];
char s[maxn];
int n, m, mx;
struct node
{
	int pos;
	ULL hash;
}p[maxn];

int cmp(node a, node b)
{
	if(a.hash == b.hash) return a.pos < b.pos;
	else return a.hash < b.hash;
}
bool search(int k)
{
	for(int i = 0; i <= n - k; i++) {
		p[i].pos = i;
		p[i].hash = hash[i] - hash[i+k] * xp[k];
	}
	sort(p, p + n-k+1, cmp);
	mx = -1;
	int cnt = 1;
	for(int i = 1; i <= n - k; i++) {
		if(cnt >= m) mx = max(mx, p[i-1].pos);
		if(p[i].hash == p[i-1].hash) cnt++;
		else cnt = 1;
	} 
	if(cnt >= m) mx = max(mx, p[n-k].pos);
	if(mx >= 0) return true;
	else return false;
}
void work(void)
{
	n = strlen(s);
	xp[0] = 1, hash[n] = 0;
	for(int i = 1; i <= n; i++) xp[i] = xp[i-1] * x;
	for(int i = n-1; i >= 0; i--) hash[i] = hash[i+1] * x + s[i] - 'a';
	if(!search(1)) {
		printf("none\n");
		return;
	}
	int bot = 1, top = n, mid, res;
	while(top >= bot) {
		mid = (top + bot) >> 1;
		if(search(mid)) bot = mid + 1, res = mid;
		else top = mid - 1;
	}
	search(res);
	printf("%d %d\n", res, mx);
}
int main(void)
{
	while(scanf("%d", &m), m != 0) {
		scanf("%s", s);
		work();
	}
	return 0;
}