Create 1247-minimum-swaps-to-make-strings-equal.js

Author: everthis

1247-minimum-swaps-to-make-strings-equal.js

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+/**
+ * @param {string} s1
+ * @param {string} s2
+ * @return {number}
+ */
+const minimumSwap = function (s1, s2) {
+  let x1 = 0 // number of 'x' in s1 (skip equal chars at same index)
+  let y1 = 0 // number of 'y' in s1 (skip equal chars at same index)
+  let x2 = 0 // number of 'x' in s2 (skip equal chars at same index)
+  let y2 = 0 // number of 'y' in s2 (skip equal chars at same index)
+
+  for (let i = 0; i < s1.length; i++) {
+    let c1 = s1.charAt(i)
+    let c2 = s2.charAt(i)
+    if (c1 == c2) {
+      // skip chars that are equal at the same index in s1 and s2
+      continue
+    }
+    if (c1 == 'x') {
+      x1++
+    } else {
+      y1++
+    }
+    if (c2 == 'x') {
+      x2++
+    } else {
+      y2++
+    }
+  } // end for
+
+  // After skip "c1 == c2", check the number of  'x' and 'y' left in s1 and s2.
+  if ((x1 + x2) % 2 != 0 || (y1 + y2) % 2 != 0) {
+    return -1 // if number of 'x' or 'y' is odd, we can not make s1 equals to s2
+  }
+
+  let swaps = Math.floor(x1 / 2) + Math.floor(y1 / 2) + (x1 % 2) * 2
+  // Cases to do 1 swap:
+  // "xx" => x1 / 2 => how many pairs of 'x' we have ?
+  // "yy" => y1 / 2 => how many pairs of 'y' we have ?
+  //
+  // Cases to do 2 swaps:
+  // "xy" or "yx" =>  x1 % 2
+
+  return swaps
+}