给定一个字符串,我们必须检查最长前缀的长度,它也是字符串的后缀,就像有一个字符串“abcab”,所以这里“ab”的长度为2,是最长的子字符串相同的前缀和后缀。
示例
Input: str[] = { “aabbccdaabbcc” }
Output: 6
Input: abdab
Output: 2
如果我们从字符串的开头和结尾开始指针,那么它们会在某个点重叠,所以我们不会这样做,而是从中间断开字符串并开始匹配左右字符串。如果它们相等,则任何一个匹配字符串的返回大小相同,否则尝试两侧的长度较短。
算法
int longest(char str[], int n)
START
STEP 1 : DECLARE length AS 0 AND i AS n/2
STEP 2 : IF n < 2 THEN
RETURN 1
STEP 3 :LOOP WHILE TILL str[i]!='0'
IF str[i] == str[length] THEN,
INCREMENT length BY 1
INCREMENT i BY 1
ELSE
IF length == 0 THEN,
INCREMENT i BY 1
ELSE
DECREMENT length BY 1
END IF
END IF
END WHILE
RETURN length
STOP
示例
#include <stdio.h>
int longest(char str[], int n){
int length = 0, i = n/2;
if( n < 2 )
return 1;
while( str[i]!='0' ){
//When we find the character like prefix in suffix,
//we will move the length and i to count the length of the similar prefix and suffix
if (str[i] == str[length]){
++length;
++i;
} else //When prefix and suffix not equal{
if(length == 0)
++i;
else
--length;
}
}
return length;
}
int main(int argc, char const *argv[]){
char str[] = {"abccmmabcc"};
int n = sizeof(str)/sizeof(str[0]);
int length = longest(str, n);
printf("Length = %d", length);
return 0;
}
输出
如果我们运行上面的程序,它将生成以下输出:
Length = 4