ACM -- 算法小结（四）KMP(POJ3461)

    KMP -- POJ3461解题报告

问题描述：给出字符串P和字符串T，问字符串P在字符串T中出现的次数

Sample Input
3
BAPC
BAPC
AZA
AZAZAZA
VERDI
AVERDXIVYERDIAN

Sample Output
1
3
0

简单KMP应用， 代码如下：

//poj3461解题报告
#include<iostream>
using namespace std;

char T[1000005], P[10005];
int len1, len2;
int next[10005];

void getnext(char P[])
{
    int i = 0, j = -1;
    next[0] = -1;
    while(i < len2)
    {
        if(j == -1 || P[i] == P[j])
        {
            i ++;
            j ++;
            next[i] = j;
        }
        else
            j = next[j];
    }
}

int kmp()
{
    int i = 0, j = 0;
    int count = 0;
    for(i = 0; i < len1; i ++)
    {
        while(j > 0 && T[i] != P[j])
            j = next[j];
        if(T[i] == P[j])
            j++;
        if(j == len2)
        {
            count ++;
            j = next[j];
        }
    }
    return count;
}

int main()
{
    int t;
    while(scanf("%d", &t) != EOF)
    {
        for(int i = 1; I <= t; i ++)
        {
            scanf("%s%s", P, T);
            int count = 0;
            len1 = strlen(T);
            len2 = strlen(P);
            getnext(P);
            int k = kmp();
            printf("%d
", k);
        }
    }
    return 0;
}