light oj 1255 - Substring Frequency (KMP)

//light oj 1255 - Substring Frequency (KMP)
//2013-05-13-19.12
#include <stdio.h>
#include <string.h>
const int maxn = 1000006;

char a[maxn];
char b[maxn];
int f[maxn];

void getfail()
{
int l = strlen(b);
f[0] = 0;
f[1] = 0;
for (int i = 1; i < l; i++)
{
int j = f[i];
while (j && b[i] != b[j])
j = f[j];
if (b[i] == b[j])
f[i+1] = j+1;
else
f[i+1] = 0;
}
}

int kmp()
{
int ans = 0;
int la = strlen(a);
int lb = strlen(b);
getfail();
int j = 0;
for (int i = 0; i < la; i++)
{
while (j && a[i] != b[j])
j = f[j];
if (b[j] == a[i])
j++;
if (j == lb)
ans++;
}
return ans;
}

int main()
{
int t;
scanf("%d", &t);
for (int i = 1; i <= t; i++)
{
scanf("%s %s", a, b);
printf("Case %d: %d\n", i, kmp());
}
return 0;
}