【字符串hash】 HDOJ 1381 Crazy Search

简单字符串hash。。。。用一下STL即可。。。

#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 10000005#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);}//headconst int x = 123;ULL hash[maxn], xp[maxn];map<ULL, int> mpp;char s[maxn];int n, m;void read(void){scanf("%d%*d", &m);scanf("%s", s);n = strlen(s);}inline ULL H(int now, int L){return hash[now] - hash[now+L] * xp[L];}void work(void){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';int tt = n - m, ans = 0;mpp.clear();for(int i = 0; i <= tt; i++) {ULL t = H(i, m);if(!mpp.count(t)) mpp[t] = 1, ans++;}printf("%d\n", ans);}int main(void){int _;while(scanf("%d", &_)!=EOF) {read();work();}return 0;}