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1071. Greatest Common Divisor of Strings

Description

For two strings s and t, we say "t divides s" if and only if s = t + ... + t (i.e., t is concatenated with itself one or more times).

Given two strings str1 and str2, return the largest string x such that x divides both str1 and str2.

 

Example 1:

Input: str1 = "ABCABC", str2 = "ABC"
Output: "ABC"

Example 2:

Input: str1 = "ABABAB", str2 = "ABAB"
Output: "AB"

Example 3:

Input: str1 = "LEET", str2 = "CODE"
Output: ""

 

Constraints:

  • 1 <= str1.length, str2.length <= 1000
  • str1 and str2 consist of English uppercase letters.

Solutions

  • class Solution {
        public String gcdOfStrings(String str1, String str2) {
            if (!(str1 + str2).equals(str2 + str1)) {
                return "";
            }
            int len = gcd(str1.length(), str2.length());
            return str1.substring(0, len);
        }
    
        private int gcd(int a, int b) {
            return b == 0 ? a : gcd(b, a % b);
        }
    }
    
  • class Solution {
    public:
        string gcdOfStrings(string str1, string str2) {
            if (str1 + str2 != str2 + str1) return "";
            int n = __gcd(str1.size(), str2.size());
            return str1.substr(0, n);
        }
    };
    
  • class Solution:
        def gcdOfStrings(self, str1: str, str2: str) -> str:
            def check(a, b):
                c = ""
                while len(c) < len(b):
                    c += a
                return c == b
    
            for i in range(min(len(str1), len(str2)), 0, -1):
                t = str1[:i]
                if check(t, str1) and check(t, str2):
                    return t
            return ''
    
    
  • func gcdOfStrings(str1 string, str2 string) string {
    	if str1+str2 != str2+str1 {
    		return ""
    	}
    	n := gcd(len(str1), len(str2))
    	return str1[:n]
    }
    
    func gcd(a, b int) int {
    	if b == 0 {
    		return a
    	}
    	return gcd(b, a%b)
    }
    
  • impl Solution {
        pub fn gcd_of_strings(str1: String, str2: String) -> String {
            if str1.clone() + &str2 != str2.clone() + &str1 {
                return String::from("");
            }
            fn gcd(a: usize, b: usize) -> usize {
                if b == 0 {
                    return a;
                }
                gcd(b, a % b)
            }
    
            let (m, n) = (str1.len().max(str2.len()), str1.len().min(str2.len()));
            str1[..gcd(m, n)].to_string()
        }
    }
    
    

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