数据结构实验4——字符串匹配

挺好写的

贴代码：

#include <iostream>
#include <cstdio>
#include <windows.h>
#include <cwchar>

using namespace std;

const int max_str_len = 255;//用户在255（1字节）以内定义最大串长
typedef char SString[max_str_len];//0号单元存放串的长度

//生成一个值等于chars的串T
void StrAssign(SString T, char * chars){
    for(int i = 0; chars[i] != '\0'; i ++ ){
        T[i + 1] = chars[i];
        T[0] = char(i + 1);
    }
}

void StrPrint(SString T){
    int len = (int)T[0];
    for(int i = 1; i <= len; i ++ ){
        printf("%c", T[i]);
    }
    cout<<endl;
}

int StrLength(SString S){
    int len = (int)S[0];
    return len;
}

bool Concat(SString T, SString S1, SString S2){
    int len1 = (int)S1[0];
    int len2 = (int)S2[0];
    if(len1 + len2 > max_str_len) return false;
    T[0] = char(len1 + len2);
    for(int i = 1; i <= len1; i ++ ){
        T[i] = S1[i];
    }
    for(int i = len1 + 1; i <= len1 + len2; i ++ ){
        T[i] = S2[i - len1];
    }
    return true;
}

//BF算法（暴力
//返回子串t在主串中第pos个字符开始第一次出现的位置。若不存在，则返回值为0
//t非空， 1 <= pos <= s.length
int index(SString s, SString t, int pos){
    int i = pos, j = 1;
    while(i <= StrLength(s) && j <= StrLength(t)){
        if(s[i] == t[j]){
            i ++ ;
            j ++ ;
        }
        else{
            i = i - j + 2;
            j = 1;
        }
    }
    if(j > StrLength(t))
        return i - StrLength(t);
    else return 0;
}

//求next数组
void get_next(SString t, int next[]){
    int i = 1;
    next[1] = 0;
    int j = 0;
    while(i < StrLength(t)){
        if(j == 0 || t[i] == t[j]){
            i ++ ;
            j ++ ;
            next[i] = j;
        }
        else j = next[j];
    }
}

//kmp算法
int kmp(SString s, SString t, int pos, int next[]){
    int i = pos;
    int j = 1;
    while(i <= StrLength(s) && j <= StrLength(t)){
        if(j == 0 || s[i] == t[j]){
            i ++ ;
            j ++ ;
        }
        else
            j = next[j];
    }
    if(j > StrLength(t))
        return i - StrLength(t);
    else
        return 0;
}

int main()
{
    SetConsoleOutputCP(65001);
    int i, *next;
    char ch1[80], ch2[80];
    SString s1, s2, s, sub;//定义串，第一个单元储存串的长度
    cout<<"请输入第一个字符串:";
    cin>>ch1;
    StrAssign(s1, ch1);
    StrPrint(s1);
    cout<<"请输入第二个字符串:";
    cin>>ch2;
    StrAssign(s2, ch2);
    StrPrint(s2);
    cout<<"-------------------------\n";
    cout<<"第一个字符串长度为:"<<StrLength(s1)<<endl;
    cout<<"第二个字符串长度为:"<<StrLength(s2)<<endl;
    if(!Concat(s, s1, s2)){
        cout<<"字符串过长"<<endl;
        return 0;
    }
    else{
        cout<<"主串长度为:"<<StrLength(s)<<endl;
        cout<<"主串为:";
        StrPrint(s);
    }
    cout<<"请输入子串:";
    cin>>ch2;
    StrAssign(sub, ch2);
    cout<<"子串长度为:"<<StrLength(sub)<<endl;
    cout<<"----BE匹配算法及实现------\n";
    i = index(s, sub, 1);
    if(i)
        printf("主串和子串在第%d个字符处首次匹配\n", i);
    else
        printf("主串和子串匹配不成功\n");
    cout<<"----KMP匹配算法及实现----\n";
    next = new int[StrLength(sub) + 1];
    get_next(sub, next);
    printf("子串的next数组为:");
    for(int i = 1; i <= StrLength(sub); i ++ ){
        cout<<*(next + i);
    }
    cout<<endl;
    i = kmp(s, sub, 1, next);
    if(i)
        printf("主串和子串在第%d个字符处首次匹配\n", i);
    else
        printf("主串和子串匹配不成功\n");
    return 0;
}