KMP算法-C语言程序实现

原理参考ACM算法训练教程一书

//////////////////////////////////////////////////
/*KMP算法*/
#include<stdio.h>
#include<string.h>
#include<iostream>
using namespace std;

void getNext(char a[],int next[]){
	int i,j;
	next[1] = 0;
	j = 0;
	i = 2;
	int m = strlen(a)-1; //从a[1]开始
	while(i<=m){
		if(a[j+1] == a[i]){
			j++; next[i++] = j;
		}
		else if(j==0){
			next[i++] = 0;
		}else if(j>0){
			j = next[j];
		}
	}
}
int match(char a[],char b[],int next[]){
	int i=0,j=0;
	int pos;
	int n = strlen(a)-1;
	int m = strlen(b)-1;
	while(1){
		if(i>n) {
			pos = -1; break;
		}
		if(j==m){
			//pos = i-j+1; break;
			cout<<i-j+1<<"  "<<endl; j=next[j];
		}
		if(b[j+1] == a[i+1] ){
			j++; i++;
		}else{
			if(j==0) i++;
			else if (j>0){
				j = next[j];
			}
		}
	}
}
/*
int main()
{
	//char b[] = "!ababbc";
	char b[] = "!abab";
	int l = strlen(b);
	int *next = new int[l-1];
	getNext(b,next);
	int i;
	for(i=1;i<=l-1;i++){
		printf("%d ",next[i]);
	}
	cout<<endl;
	char a[] = "!ababababbc";
	int pos = match(a,b,next);
	cout<<endl<<pos<<endl;
}
*/
//////////////////////////////////////////////////////
/*
KMP应用： 求一个串中所有前缀等于后缀的子串长度
*/
void output(int i,int next[]){
	while(next[i]>0){
		cout<<next[i]<<" ";
		i = next[i];
	}
}
/*
int main()
{
	char b[] = "!ababa";
	int l = strlen(b);
	int *next = new int[l-1];
	getNext(b,next);
	int i;
	for(i=1;i<=l-1;i++){
		printf("%d ",next[i]);
	}
	cout<<endl;
	output(l-1,next);
	delete[] next;
}
*/

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