KMP函数实现

大神代码：https://blog.csdn.net/v_july_v/article/details/7041827

 

本篇是接着上一篇的理论写了一个简单的Demo，上面的链接是代码的原地址，下面是我写的Demo，供大家参考。

2. 匹配函数

int KMPSearch(char* a,char* p,int * next){
	int a_len = strlen(a);
	int p_len = strlen(p);
	int i=0, j=0;

	while (i < a_len&&j < p_len){
		if (j >= 0){
			cout << "after : a[i] is : " << a[i] << ", p[j] is : " << p[j] << ", i is : " << i << ", j is : " << j << endl;
		}else{
			cout << "after : a[i] is : " << a[i] << ", p[j] is : ** " <<  ", i is : " << i << ", j is : " << j << endl;
		}
		
		if (j == -1 || a[i] == p[j]){
			++i;
			++j;
		}
		else
		{
			j = next[j];
		}		
	}
	if (j == p_len){
		return i - j;
	}
	else{
		return -1;
	}
}

下面是程序汇总

 

#include "stdafx.h"
#include "iostream"
using namespace std;

void Next(char * a,int * next){
	int n = strlen(a);
	next[0] = -1;
	int k = -1;
	int j = 0;
	while (j= 0){
			cout << "after : a[i] is : " << a[i] << ", p[j] is : " << p[j] << ", i is : " << i << ", j is : " << j << endl;
		}else{
			cout << "after : a[i] is : " << a[i] << ", p[j] is : ** " <<  ", i is : " << i << ", j is : " << j << endl;
		}
		
		if (j == -1 || a[i] == p[j]){
			++i;
			++j;
		}
		else
		{
			j = next[j];
		}

		
	}
	if (j == p_len){
		return i - j;
	}
	else{
		return -1;
	}

}

int _tmain(int argc, _TCHAR* argv[])
{
	char a[] = "abab";
	char p[] = "abacabayabab";
	int n = strlen(a);
	int next[4] = { -2};
	Next(a,next);
	int Pos = KMPSearch(p, a, next);

	return 0;
}