Substring Frequency （KMP）

Substring Frequency

Time Limit:1000MS     Memory Limit:65536KB     64bit IO Format:%lld & %llu

Submit Status Practice LightOJ 1255

Description

A string is a finite sequence of symbols that are chosen from an alphabet. In this problem you are given two non-empty strings A and B, both contain lower case English alphabets. You have to find the number of times B occurs as a substring of A.

Input

Input starts with an integer T (≤ 5), denoting the number of test cases.

Each case starts with two lines. First line contains A and second line contains B. You can assume than 1 ≤ length(A), length(B) ≤ 10⁶.

Output

For each case, print the case number and the number of times B occurs as a substring of A.

Sample Input

4

axbyczd

abc

abcabcabcabc

abc

aabacbaabbaaz

aab

aaaaaa

aa

Sample Output

Case 1: 0

Case 2: 4

Case 3: 2

Case 4: 5

Hint

Dataset is huge, use faster I/O methods.

算法：KMP

#include <iostream>
#include <string>
#include <cstdio>
#include <cstring>
using namespace std;

const int maxn = 1000001;
char pattern[maxn], target[maxn];
int prefix[maxn];
int lenp, lent;
int cnt, t, ca;

void GetPrefix()
{
    int i = 0, j = -1;
    prefix[0] = -1;
    while(i < lenp)
    {
        if(j == -1 || pattern[i] == pattern[j])
        {
            i++;
            j++;
            prefix[i] = j;
        }
        else j = prefix[j];
    }
}

void KMP()
{
    GetPrefix();
    int i = 0, j = 0;
    while(i < lent)
    {
        if(target[i] == pattern[j] || j == -1)
        {
            j++;
            i++;
        }
        else j = prefix[j];
        if(j == lenp)
        {
            j = prefix[j];
            cnt++;
        }
    }
}

int main()
{
    scanf("%d", &t);
    ca = 1;
    while(t--)
    {
        scanf("%s %s", target, pattern);
        lenp = strlen(pattern);
        lent = strlen(target);
        cnt = 0;
        KMP();
        printf("Case %d: %d\n", ca++, cnt);
    }
    return 0;
}