KMP算法我先做一个简单介绍：
朴素算法的时间复杂度N平方，而KMP是N+M。
空间复杂度都为N。
也就是这么多吧，让我们一起来看看代码：

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<cstring>
#include<algorithm>

using namespace std;

#define next Next

#define REP(i, a, b) for(i = (a);i <= (b); ++i)

const int maxn = 1000010;

int next[maxn];
char p[maxn], t[maxn], s[maxn];
int ans = 0;

void init(char s2[], char s1[]) {
    int len1 = strlen(s1);
    int len2 = strlen(s2);
    int i = 0, j = -1;
    next[0] = -1;
    while(i != len2)
        if(j == -1 || s1[i] == s1[j])
            next[++i] = ++j;
        else
            j = next[j];
} 

void KMP(char s2[], char s1[]) {
    int len1 = strlen(s1);
    int len2 = strlen(s2);
    init(s1, s2);
    int i = 0;
    int j = 0;
    while(i != len1 && j != len2) {  
        if(s1[i] == s2[j] || j == -1) {
            ++i;
            ++j;  
        }
        else  
            j = next[j];  
        if(j == len2) {  
            ++ans;  
            j = next[j];  
        }  
    }  
}

int main() {
    int m, n, i, j, k;
    int r, l;
    scanf("%s%s", &p, &t);
    int plen = strlen(p);
    int tlen = strlen(t); 
    REP(i, 0, tlen - 1) {
        l = i, r = i;
        while(l >= 0 && r < tlen && t[l] == t[r]) {
            REP(j, l, r)
                s[j - l] = t[j];
            s[r - l + 1] = '\0';
            KMP(s, p); 
            l--,r++;
        }
        l = i, r = i + 1;
        while(l >= 0 && r < tlen && t[l] == t[r]) {
            REP(j, l, r)
                s[j - l] = t[j];
            s[r - l + 1] = '\0';
            KMP(s, p);
            l--,r++;
        }
    }
    printf("%d\n", ans);
    return 0; 
}

太容易了，就不做具体介绍了。