string matching(拓展KMP)

Problem Description

String matching is a common type of problem in computer science. One string matching problem is as following:

Given a string 

We are wondering, for any given string, what is the number of compare operations invoked if we use the above algorithm. Please tell us the answer before we attempt to run this algorithm.

 

 

Input

The first line contains an integer 6 for every string

 

 

Output

For each test, print an integer in one line indicating the number of compare operations invoked if we run the algorithm in the statement against the input string.

 

 

Sample Input

3 _Happy_New_Year_ ywwyww zjczzzjczjczzzjc

 

 

Sample Output

17 7 32

代码：

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<queue>
#include<stack>
#include<set>
#include<map>
#include<vector>
#include<cmath>

const int maxn=1e6+5;
typedef long long ll;
using namespace std;

ll ans;
void pre_EKMP(char x[],int m,ll next[])
{
    next[0]=m;
    int j=0;
    while(j+1<m&&x[j]==x[j+1])
    {
        j++;
    }

    next[1]=j;
    int k=1;
    for(int i=2;i<m;i++)
    {
        int p=next[k]+k-1;
        int L=next[i-k];
        if(i+L<p+1)next[i]=L;
        else
        {
            j=max(0,p-i+1);
            while(i+j<m&&x[i+j]==x[j])j++;
        
            next[i]=j;
            k=i;
        }
    }
}

char str[10*maxn];
ll nxt[10*maxn];
int main()
{
    int T;
    cin>>T;
    
    while(T--)
    {
        scanf("%s",str);
        int len=strlen(str);
        ans=0;
    
        pre_EKMP(str,len,nxt);
        for(int t=1;t<len;t++)
        {
            if(nxt[t]+t<len)
            {
              ans+=(nxt[t]+1);
            }
            else
            {
                ans+=(len-t);
            }
        }
    //    ll ans=0;
    printf("%lld\n",ans);
    }
    return 0;
}