题解 | #公共子串计算#

#include <stdio.h>

int main()
{
    char str[2][151] = {0};
    int max_len = 0;
    
    for(int i = 0; i < 2; i++)
    {
        if(gets(str[i]) == NULL)
        {
            return 0;
        }
    }
    int len0 = strlen(str[0]);
    int len1 = strlen(str[1]);
    
    int size = 0;
    int str0_left = 0;
    int str0_right = 0;
    int str1_left = 0;
    int str1_right = 0;
    int left_stop = 0;
    int right_stop = 0;
    
    /* 遍历，左，右滑动，分别使用双指针比较 */
    for(int i = 0; i < len0; i++)
    {
        for(int j = 0; j < len1; j++)
        {
            /* 字符相等时，开始左右指针滑动比较 */
            if(str[0][i] == str[1][j])
            {
                str0_left = i - 1;
                str0_right = i + 1;
                str1_left = j - 1;
                str1_right = j + 1;
                left_stop = 1;
                right_stop = 1;
                size = 1;
            
                while(
                    (str0_left >= 0 && str1_left >= 0 &&  str[0][str0_left] == str[1][str1_left] && left_stop)
                    || (str0_right < len0 && str1_right < len1 && str[0][str0_right] == str[1][str1_right] && right_stop)
                      )
                {
                    int left_equals = 0;
                    int right_equals = 0;
                    
                    if(str0_left >= 0 && str1_left >= 0)
                    {
                        left_equals = (str[0][str0_left] == str[1][str1_left]) ? 1 : 0 ;
                        /* 左指针标识停止滑动 */
                        left_stop = left_equals;
                        
                                               
                    }
                    if(str0_right < len0 && str1_right < len1)
                    {
                        right_equals = (str[0][str0_right] == str[1][str1_right]) ? 1 : 0 ;
                        /* 右指针标识停止滑动 */
                        right_stop = right_equals;                                  
                    }
                    
                    /* 左右字符均相同，累加2 */
                    if(left_equals && right_equals)
                    {
                        size += 2;
                    }
                    else
                    {
                        size++;
                    }
                    
                    if(left_stop)
                    {
                        str0_left--;
                        str1_left--;
                    }
                    
                    if(right_stop)
                    {
                        str0_right++;
                        str1_right++;
                    }
                    
                }
                
                
                if(size > max_len)
                {
//                     printf("size = %d, i = %d, str0_left = %d, str0_right = %d \n", size, i, str0_left, str0_right);
//                     printf(" str1_left = %d, str1_right = %d \n", str1_left, str1_right);
                    max_len = size;
                }
        
            }
        }
    }
    
    printf("%d", max_len);
    
    return 0;
}