Leetcode挑战题——Repeated String Match

Repeated String Match

Given two strings A and B, find the minimum number of times A has to be repeated such that B is a substring of it. If no such solution, return -1.

For example, with A = "abcd" and B = "cdabcdab".

Return 3, because by repeating A three times (“abcdabcdabcd”), B is a substring of it; and B is not a substring of A repeated two times ("abcdabcd").

Note:
The length of A and B will be between 1 and 10000.

<?php    $str1 = "abcd";    $str2 = "cdabcdab";    function repeatedStringMatch($str1,$str2,$num = 1,$a = ''){        $str1_len = strlen($str1);        $str2_len = strlen($str2);        //判断字符串是否符号要求        if(!in_array($str1_len, range(1, 10000)) || !in_array($str2_len, range(1, 10000))){            return 'Invalid String!';        }        if($num == 1) $a = $str1;        if(strstr($str1,$str2)){            return $num;        }elseif($str1_len > 2*$str2_len && strstr($str1,$str2) === false){            return -1;        }else{            $str1 .= $a;            return repeatedStringMatch($str1,$str2,++$num,$a);//递归调用函数，累加重复数，注意这里不能用$num++        }    }    echo repeatedStringMatch($str1,$str2);?>

结果：3

若有不对之处，希望各位批评指正，谢谢！