数据结构 查找算法

数据结构 BF算法，KMP算法，KMP改进算法

#include <iostream>
#include <stdlib.h>
#include <cstring>
using namespace std;
int next[100]={0};
int BF(char *s, char *t)
{
    int i = 0, j = 0;
    int n = strlen(s);
    int m = strlen(t);
    while (i < n && j < m)
    {
        if (s[i] == t[j])
        {
            i++;
            j++;
        }
        else
        {
            i = i - j + 1;
            j = 0;
        }
    }
    if (j >= m)
        return i - j;
    else
        return -1;
}
void getnext(char *t)
{
	int i,j,k,m,n;
	j=0;
	k=-1;
	m=strlen(t);
	next[0]=-1;
	while(j<m-1)
	{
		if(k==-1||t[j]==t[k])
		{
			j++;
			k++;
			next[j]=k;
		}
		else 
			k=next[k];
	}
}
void getnextval(char *t)
{
	int i,j,k,m,n;
	j=0;
	k=-1;
	m=strlen(t);
	next[0]=-1;
	while(j<m-1)
	{
		if(k==-1||t[j]==t[k])
		{
			j++;
			k++;
			if(t[j]!=t[k])
				next[j]=k;
			else
				next[j]=next[k];
		}
		else 
			k=next[k];
	}
}
int KMP(char *s,char *t)
{
	int i,j,k,l,n,m;
	i=0;j=0;
	n=strlen(s);
	m=strlen(t);
	while(i<n&&j<m)
	{
		if(j==-1||s[i]==t[j])
		{
			i++;
			j++;
		}
		else
			j=next[j];
	}
	if(j>=m)
		return i-m;
	else return -1;	
}
void Showme()
{
    cout << "1.BF算法查找" << endl;
    cout << "2.KMP算法查找" << endl;
    cout << "3.KMP改进算法查找" << endl;
}


int main()
{
    char s1[100], s2[100];
	cout << "		查找程序" << endl;
    int f = -1;
    while (f)
    {
    	
        cout << "请输入原来字符串:" << endl;
        cin >> s1;
        cout << "请输入需要查找的字符串:" << endl;
        cin >> s2;
        Showme();
        cin >> f;
        switch (f)
        {
        case 1:
            cout << "BF算法查找:" << endl;
            cout << BF(s1, s2) << endl;
            break;
            case 2:
                cout << "KMP算法查找:" << endl;
                getnext(s2);
                cout << KMP(s1, s2) << endl;
                break;
            case 3:
                cout << "KMP改进算法查找:" << endl;
                getnextval(s2);
                cout << KMP(s1, s2) << endl;
                break;
        }
    }

    return 0;
}