【C语言】串的模式匹配

一、结果如图

 二、代码

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<iostream>
#define Maxsize 100
using namespace std;
typedef struct 
{
	char* ch;
	int length;
}HString;

void initlist(HString& L)
{
	L.ch = new char[Maxsize];
	if (!L.ch)
		exit(0);
	L.ch[0] = '#';
	L.length = 0;
	char m[Maxsize];
	int i = 0;
	cin >> m;
	while (m[i] != '\0')
	{
		L.ch[i + 1] = m[i];
		L.length++;
		i++;
	}
}
void get_next(HString T, int next[])
{
	int j = 1, k = 0;
	next[1] = 0;
	while (j < T.length)
	{
		if (k == 0 || T.ch[j] == T.ch[k])
		{
			++j;
			++k;
			next[j] = k;
		}
		else
			k = next[k];
	}
	printf("\n（1）next=");
	for (int i = 1; i <= T.length; i++)
		printf("%d ", next[i]);
	printf("\n");
}
void get_nextval(HString T, int nextval[])
{
	int j = 1, k = 0;
	nextval[1] = 0;
	while (j < T.length)
	{
		if (k == 0 || T.ch[j] == T.ch[k])
		{
			++j;
			++k;
			if (T.ch[j] != T.ch[k])
				nextval[j] = k;
			else
				nextval[j] = nextval[k];
		}
		else k = nextval[k];
	}
	printf("nextval=");
	for (int i = 1; i <= T.length; i++)
		printf("%d ", nextval[i]);
	printf("\n");
}
int index_KMP(HString S, HString T, int pos, int next[])
{
	int i = pos;
	int j = 1;
	int m = 0;//初始化比较次数m
	while (i <= S.length && j <= T.length) 
	{
		if (j == 0 || S.ch[i] == T.ch[j])
		{
			i++;
			j++;
		}
		else
			j = next[j];
		m++;
	}
	if (j > T.length)
		printf("index_KMP= %d\n", i - T.length);
	else
		printf("index_KMP = 0\n");
	return m;
}
int index_BF(HString S, HString T, int pos)
{
	int i = pos;
	int j = 1;
	int m = 0;
	while (i <= S.length && j <= T.length)
	{
		if (S.ch[i] == T.ch[j]) {
			i++;
			j++;
		}
		else
		{
			i = i - j + 2;
			j = 1;
		}
		m++;
	}
	if (j > T.length)
		printf("\n（2）匹配成功位置：\nindex_BF = %d", i - T.length);
	else
		printf("\n匹配成功位置：\nindex_BF = 0");
	return m;
}
void result(HString S, HString T)
{
	int pos;
	int a, b, c;
	int next[Maxsize] = { 0 };
	int nextval[Maxsize] = { 0 };
	printf("主串中匹配开始位置pos( <=%d ) = ", S.length);
	scanf_s("%d", &pos);
	printf("\n***************结果栏***************\n");
	get_next(T, next);
	get_nextval(T, nextval);
	a = index_BF(S, T, pos);
	printf("\n\n用next函数值：");
	b = index_KMP(S, T, pos, next);
	printf("用nextval函数值：");
	c = index_KMP(S, T, pos, nextval);
	printf("\n（3）比较次数\nBF算法：%d", a);
	printf("\nKMP算法用next函数值：%d；\nKMP算法用nextval函数值：%d\n", b, c);
	if (a > c)
		printf("\n（4）效率：KMP算法 > BF算法\n");
	else if (a == c)
		printf("\n（4）效率：KMP算法 = BF算法\n");
	else
		printf("\n（4）效率：KMP算法 < BF算法\n");
}
void main()
{
	int flag = 1;
	while (flag == 1) {
		HString S, T;
		printf("\n***************输入栏***************\n");
		printf("主串S：");
		initlist(S);
		printf("子串T：");
		initlist(T);
		result(S, T);
		printf("\n\n***************提示栏***************\n");
		printf("是否重新进行？是按1，否按2.\n请选择：");
		scanf_s("%d", &flag);
		if (flag != 1)
			printf("\n*************程序已结束*************\n");
	}
}