POJ 3461 Oulipo（字符串hash）

题目链接

字符串hash判断字符串是否相等。

code

 #include<cstdio>
 #include<algorithm>
 #include<cstring>

 using namespace std;

 typedef unsigned long long uLL;
 const uLL B = ;

 uLL f[];
 uLL Hash[];
 char a[],b[];

 int main () {
     int T;
     scanf("%d",&T);
     f[] = ;
     for (int i=; i<=; ++i) f[i] = (f[i-] * B);
     while (T--) {
         int ans = ;
         scanf("%s%s",a,b);
         int s1 = strlen(a),s2 = strlen(b);
         uLL Ha = ;
         for (int i=; i<s1; ++i) {
             Ha = (Ha*B+a[i]);
         }
         Hash[] = b[];
         for (int i=; i<s2; ++i) {
             Hash[i] = Hash[i-]*B+b[i];
         }
         for (int i=; i<=(s2-s1); ++i) {
             int l = i,r = l+s1-;
             uLL Hb = Hash[r]-Hash[l-]*f[s1];
             if (Ha == Hb) ans++;
         }
         printf("%d\n",ans);
     }
     return ;
 }