KMP和BF算法-C语言实现

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <malloc.h>
//以下为KMP算法
void get_next(char * T, int next[])   //修正前的next数组
{
	int i = 1, j = 0;
	next[0] = -1;
	next[1] = 0;
	int m = strlen(T);
	while (i<strlen(T) - 1)
	{
		if (j == -1 || T[j] == T[i])
		{
			++i;
			++j;
			next[i] = j;
		}
		else j = next[j];
	}
}
void get_nextval(char * T, int nextval[]) //修正后的nextval数组
{
	int i = 1, j = 0;
	nextval[0] = -1;
	nextval[1] = 0;
	int m = strlen(T);
	while (i<strlen(T) - 1)
	{
		if (j == -1 || T[j] == T[i])
		{
			++i;
			++j;
			if (T[i] != T[j]) nextval[i] = j;
			else nextval[i] = nextval[j];
		}
		else j = nextval[j];
	}
}
int Index_KMP(char * S, char * T, int pos, int next[])   //逐项比较
{
	int j = 0, i = pos, lens = strlen(S), lent = strlen(T);
	get_next(T, next);
	while (i < lens && j < lent)
	{
		if (S[i] == T[j] || j == -1)
		{
			i++; j++;
		}
		else j = next[j];
	}
	if (j >= lent) return i - lent;
	else return -1;
}

//以下为BF算法
int Pos_BF(char * S, char * T)
{
	int pos = 1;
	for (int i = 0; i < strlen(S); i++)
	{
		if (S[i] == T[0])
			return pos;
		else
			pos++;
	}
	return 0;
}
int Index_BF(char * S, char * T)
{
	int i = 0, j = 0;
	int lens = strlen(S), lent = strlen(T);
	while (i <= lens -1  && j <= lent -1 )
	{
		if (S[i] == T[j])
		{
			++i;
			++j;
		}
		else
		{
			i = i - j + 1;
			j = 0;
		}
	}
	//跳出循环有两种可能，i=lens说明已经遍历完主串，匹配失败；j=lent,说明子串遍历完成，在主串中成功匹配
	if (j == lent) {
		return i - lent + 1;
	}
	//运行到此，为i==lens的情况
	return -1;
}


int main()
{
	//char *S = "adbadabbaabadabbadada", *T = "adabbadada";
	char S[30];
	char T[20];
	printf("请输入两个字符串进行匹配：
");
	printf("请输入母串：");
	scanf("%s", S);
	printf("请输入匹配串：");
	scanf("%s", T);
	//此处开始测试KMP算法
	printf("
**********************KMP算法**************************
");
	int m;
	int *next = (int *)malloc((strlen(T) + 1)*sizeof(int));   //修正前的next数组
	int *nextval = (int *)malloc((strlen(T) + 1)*sizeof(int));    //修正后的nextval数组
	get_next(T, next);
	printf("修正前next数组为：");
	for (m = 0; m<strlen(T); m++)
	{
		printf("%d ", next[m] + 1);
	}
	get_nextval(T, nextval);
	printf("
修正后的nextval数组为：");
	for (m = 0; m<strlen(T); m++)
	{
		printf("%d ", nextval[m] + 1);
	}
	int t1 = Index_KMP(S, T, 0, nextval);
	if (t1 == -1) printf("
无匹配项！
");
	else
	{
		printf("
在第%d项开始匹配成功
", t1 + 1);
	}
	//此处开始测试BF算法
	printf("
**********************BF算法**************************
");
	int t2 = Index_BF(S, T);
	printf("
在第%d项开始匹配成功
", t2);
	system("pause");
	return 0;
}