Create greatest-common-divisor-of-strings.cpp

Author: kamyu104

C++/greatest-common-divisor-of-strings.cpp

@@ -0,0 +1,35 @@
+// Time:  O(m + n)
+// Space: O(1)
+
+class Solution {
+public:
+    string gcdOfStrings(string str1, string str2) {
+        if (str1.empty() || str2.empty()) {
+            return "";
+        }
+        int c = gcd(str1.length(), str2.length());
+        const auto& result = str1.substr(0, c);
+        return check(str1, result) && check(str2, result) ? result : "";
+    }
+
+private:
+    bool check(const string& s, const string& common) {
+        int i = 0;
+        for (const auto& c : s) {
+            if (c != common[i]) {
+                return false;
+            }
+            i = (i + 1) % common.length();
+        }
+        return true;
+    }
+
+    int gcd(int a, int b) {
+        while (b != 0) {
+            int tmp = b;
+            b = a % b;
+            a = tmp;
+        }
+        return a;
+    }
+};