返回子字符串的个数

题目：已知一个字符串，比如asderwsde，寻找其中的一个子字符串比如sde的个数，如果没有返回0，有的话返回子字符串的个数。

答：

#include "stdafx.h"
#include <iostream>

using namespace std;

//获取next数组的值
void GetNext(const char* pattern, int length, int *next)
{
    int i = 0;
    next[i] = -1;
    int j = -1;
    while (i < length - 1)
    {
        if (-1 == j || pattern[i] == pattern[j])
        {
            i++;
            j++;
            if (pattern[i] != pattern[j])
            {
                next[i] = j;
            }
            else
            {
                next[i] = next[j];
            }
        }
        else
        {
            j = next[j];
        }
    }
}

//返回子字符串的个数
int CountSubstringNumber(const char *src, int slength, const char * pattern, int plength, int *next)
{
    int i = 0;
    int j = 0;
    int count = 0;
    while (i < slength && j < plength)
    {
        if (-1 == j || src[i] == pattern[j])
        {
            i++;
            j++;
        }
        else
        {
            j = next[j];
        }
        if (j >= plength)
        {
            count++;
            j = 0;
        }
    }

    return count;
}

int _tmain(int argc, _TCHAR* argv[])
{
    char src[] = "asderwsde";
    char pattern[] = "sde";
    int slength =strlen(src);
    int plength = strlen(pattern);
    int *next = new int[plength];
    GetNext(pattern, plength, next);
    int pos = CountSubstringNumber(src, slength, pattern, plength, next);
    cout<<"主串"<<src<<"含有子串"<<pattern<<"的个数为："<<pos<<endl;

    cout<<endl;
    return 0;
}

运行界面如下：