kmp poj 3461

这是一道KMP的水题，还没明白KMP是怎么回事 ==，先贴了代码，明天继续研究。

#include <stdio.h>
#include <string.h>

const int MaxN = 1000010;
char word[MaxN/10], txt[MaxN];
int next[MaxN/10];

void KMP_next(char b[], int pre[])
{
    int n = (int)strlen(b), k;
    pre[0] = -1; k = -1;
    for(int i = 1; i < n; i++)
    {
        while(k > -1 && b[k+1] != b[i]) k = pre[k];
        if(b[k+1] == b[i]) k++;
        pre[i] = k;
    }
}

int main()
{
    int n;
    for(scanf("%d%*c", &n); n--;)
    {
        gets(word); gets(txt);
        KMP_next(word, next);
        int cnt = 0, len = (int)strlen(word);
        for(int i = 0, j = -1; txt[i]; ++i)
        {
             while(j > -1 && word[j+1] != txt[i])
                 j = next[j];
             if(word[j+1] == txt[i])
                 j++;
             if(j == len-1) {
                 cnt++; j = next[j];
             }
         }
         printf("%d\n", cnt);
     }
     return 0;
}