[kuangbin带你飞]专题十六 KMP & 扩展KMP & Manacher K （kmp扩展）

https://vjudge.net/contest/70325#problem/K  HDU 3336

题意：求字符串所有前缀在原串出现的次数

思路：对自己求extend数组，遍历一遍相加就是结果.

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int maxn=200000+5;char mode[maxn];int nextt[maxn];void getNext(char mode[],int nextt[],int modeLen){int i,a,p;a=p=0;nextt[0]=modeLen;for(i=1;i<modeLen;i++){if(i>=p || i+nextt[i-a]>=p){if(i>=p) p=i;while(p<modeLen && mode[p]==mode[p-i]) ++p;nextt[i]=p-i;a=i;}else nextt[i]=nextt[i-a];}}int main(){int T;scanf("%d",&T);while(T--){int n;scanf("%d",&n);for(int i=0;i<n;i++){scanf(" %c",&mode[i]);}mode[n]='\0';int modeLen=strlen(mode);getNext(mode,nextt,modeLen);long long  ans=0;for(int i=0;i<modeLen;i++){ans=(ans+nextt[i]%10007)%10007;}printf("%lld\n",ans);}return 0;}