Today I have done leetcode's February LeetCoding Challenge with cpp.

February LeetCoding Challenge 1

Description

Greatest Common Divisor of Strings

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.

Solution

class Solution {
public:
  string gcdOfStrings(string str1, string str2) {
    if(str1.length() < str2.length()) {
      swap(str1, str2);
    }

    int pos1 = 0;
    int pos2 = 0;
    int len1 = str1.length();
    int len2 = str2.length();
    while(pos1 < len1) {
      if(str1[pos1] != str2[pos2]) return "";
      pos1 += 1;
      pos2 = (pos2 + 1) % len2;
    }
    if(pos2 == 0) return str2;
    return gcdOfStrings(str2, str2.substr(pos2));
  }
};

// Accepted
// 114/114 cases passed (3 ms)
// Your runtime beats 83.39 % of cpp submissions
// Your memory usage beats 78.21 % of cpp submissions (7.1 MB)