KMP算法

#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];
        }
    }
}

//KMP算法
int KMP(const char *src, int slength, const char * pattern, int plength, int *next)
{
    int i = 0;
    int j = 0;
    while (i < slength && j < plength)
    {
        if (-1 == j || src[i] == pattern[j])
        {
            i++;
            j++;
        }
        else
        {
            j = next[j];
        }
    }
    if (j >= plength)
    {
        return i - plength;
    }
    return -1;
}


int _tmain(int argc, _TCHAR* argv[])
{
    char src[] = "abcdababcdaedfghtevb";
    char pattern[] = "ababc";
    int plength = strlen(pattern);
    int *next = new int[plength];
    GetNext(pattern, plength, next);
    cout<<"主串："<<src<<endl;
    cout<<"子串："<<pattern<<endl;
    cout<<"子串在主串的首次匹配的位置："<<KMP(src, strlen(src), pattern, plength, next)<<endl;
    delete [] next;

    cout<<endl;
    return 0;
}

运行界面如下：