找出两个字符串中最大公共子字符串，如"abccade"、"dgcadde"的最大子串为"cad"

//// 此题用for能控制循环

int GetCommon(char *s1, char *s2, char **r1, char **r2)

{

int len1 = strlen(s1);

int len2 = strlen(s2);

int maxlen = 0;

for(int i = 0; i < len1; i++)

{

for(int j = 0; j < len2; j++)

{

if(s1[i] == s2[j]) //找到了第一个相等的

{

int as = i, bs = j, count = 1; // 保存第一个相等的首地址

while(as + 1 < len1 && bs + 1 < len2 && s1[++as] == s2[++bs]) //查找最大相等长度

count++;

if(count > maxlen) //如果大于最大长度则更新

{

maxlen = count;

*r1 = s1 + i;

*r2 = s2 + j;

}

}

}

}

下面是我的程序：

#include <stdio.h>

#include <string.h>

#include <malloc.h>

char *find_common(char *str1, char *str2)

{

int as,bs,i = 0,j = 0;//记录字符移动位置

int maxlen = 0,count; //记录最大公共子串的长度

int len1 = 0,len2 = 0;//保存待测字符的长度

char *string;//保存最大公共子串

while(*(str1 + len1) != '\0')

{

len1++;

}

while(*(str2 + len2) != '\0')

{

len2++;

}

string = (char *)malloc(len1 > len2 ? len1 : len2);//动态分配内存

for(i=0; i<len1; i++)

for(j=0; j<len2; j++)

{

if(*(str1 + i) == *(str2 + j))

{

as = i;

bs = j;

count = 1;

while(as + 1 < len1 && bs + 1 < len2 && str1[++as] == str2[++bs]) //查找最大相等长度

count++;

if(count > maxlen)

{

maxlen = count;

strncpy(string, str1+i, maxlen);

}

}

*(string + maxlen) = '\0';

}
return string;

}

int main()

{

char *str1 = NULL;

char *str2 = NULL;

char *maxstring;

str1 =(char *)malloc(256);

str2 =(char *)malloc(256);

printf("Please input the first string:");

scanf("%s",str1);

printf("Please input the second string:");

scanf("%s",str2);

maxstring = find_common(str1, str2);

printf("The maxlen is: %s\n",maxstring);

free(maxstring);

free(str2);

free(str1);

return 0;

}