Create minimum-swaps-to-make-strings-equal.cpp

Author: kamyu104

C++/minimum-swaps-to-make-strings-equal.cpp

@@ -0,0 +1,22 @@
+// Time:  O(n)
+// Space: O(1)
+
+class Solution {
+public:
+    int minimumSwap(string s1, string s2) {
+        int x1 = 0, y1 = 0;
+        for (int i = 0; i < s1.length(); ++i) {
+            if (s1[i] == s2[i]) {
+                continue;
+            }
+            x1 += int(s1[i] == 'x');
+            y1 += int(s1[i] == 'y');
+        }
+        if (x1 % 2 !=  y1 % 2) {  // impossible
+            return -1;
+        }
+        // case1: per xx or yy needs one swap, (x1 / 2 + y1 / 2) 
+        // case2: per xy or yx needs two swaps, (x1 % 2 + y1 % 2)
+        return x1 / 2 + y1 / 2 + x1 % 2 + y1 % 2;
+    }
+};