JZOJ4876. 【NOIP2016提高A组集训第10场11.8】基因突变（2017.8B组）

https://jzoj.net/senior/#main/show/4876
想法：
拓展KMP的next数组的和

#include <cstring>#include <cmath>#include <cstdio>#include <cstdlib>#include <ctime>#include <iostream>#define maxn 1000010#define ll long longusing namespace std;char s[maxn];ll next[maxn],i,j,p,a,n,ans;int main(){//  freopen("gene.in","r",stdin);//  freopen("gene.out","w",stdout);    scanf("%s",s+1);    n=strlen(s+1);    p=0;    j=-1;    next[0]=n;    a=0;    for (i=1;i<n;i++)    {        if ((j<0)||(i+next[i-a]>=p))        {            if (j<0)            {                j=0;                p=i;                }               while ((j<n)&&(p<n)&&(s[j+1]==s[p+1]))            {                j++;                p++;            }            next[i]=j;            a=i;        }         else next[i]=next[i-a];        j--;    }     for (i=0;i<n;i++)        ans+=next[i];    printf("%lld\n",ans); }