【MAC 上学习 C++】Day 54-4. 实验11-1-8

实验11-1-8 查找子串 (20 分)

1. 题目摘自

https://pintia.cn/problem-sets/13/problems/593

2. 题目内容

本题要求实现一个字符串查找的简单函数。

函数接口定义：

char *search( char *s, char *t );
函数search在字符串s中查找子串t，返回子串t在s中的首地址。若未找到，则返回NULL。

输入样例1：

The C Programming Language
ram

输出样例1：

10

输入样例2：

The C Programming Language
bored

输出样例2：

-1

3. 源码参考

#include <iostream>

using namespace std;

#define MAXS 30

char *search(char *s, char *t);
void ReadString( char s[] );

int main()
{
    char s[MAXS], t[MAXS], *pos;

    ReadString(s);
    ReadString(t);
    pos = search(s, t);

    if ( pos != NULL )
    {
      cout << pos - s << endl;
    }
    else
    {
      cout << "-1" << endl;
    }

    return 0;
}

char *search(char *s, char *t)
{
  char *p = NULL, *q = NULL;
  int iSucc;

  iSucc = 0;
  while(*s != '\0')
  {
    while((*s != '\0') && (*t != '\0') && (*s != *t))
    {
      s++;
    }

    if(*s == '\0')
    {
      break;
    }

    p = s;
    q = t;
    while((*p != '\0') && (*q != '\0') && (*p == *q))
    {
      p++;
      q++;
    }

    if(*q == '\0')
    {
      iSucc = 1;
      break;
    }

    s++;
  }

  if(iSucc != 1)
  {
    return NULL;
  }

  return s;
}

void ReadString( char s[] )
{
  cin.getline(s, MAXS, '\n');
  return;
}