CodeForces 7D Palindrome Degree 字串hash

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題目連結：點擊開啟連結

#include<stdio.h>#include<iostream>#include<string.h>#include<set>#include<vector>#include<map>#include<math.h>#include<queue>#include<string>#include<stdlib.h>#include<algorithm>using namespace std;#define N 5001000#define mod 1000000007#define hehe 137731735#define ll __int64ll n;char s[N];ll x[N], y[N];ll dp[N];int main(){ll i,j;while(gets(s)) {dp[0] = 0;for(i=0;s[i];i++) {if('0'<=s[i]&&s[i]<='9')s[i] = s[i]-'0';else if('a'<=s[i]&&s[i]<='z')s[i] = s[i]-'a'+10;else s[i] = s[i]-'A'+36;}ll len = i;x[0] = 0;ll dou = 1;for(i=1;i<=len;i++){ x[i] = (x[i-1]+s[i-1]*dou)%mod; dou = (dou*hehe)%mod; }y[len+1] = 0;for(i=1;i<=len;i++) { y[i] = (y[i-1]*hehe+s[i-1])%mod;}ll ans = 0;for(i=1;i<=len;i++) if(x[i]==y[i]) {dp[i] = dp[i>>1]+1;ans += dp[i];}cout<<ans<<endl;}return 0;}