Add solution #3431

JoshCrozier · JoshCrozier · commit e5ca5ef79505 · 2025-07-23T23:52:39.000-05:00
diff --git a/README.md b/README.md
@@ -2692,6 +2692,7 @@
 3416|[Subsequences with a Unique Middle Mode II](./solutions/3416-subsequences-with-a-unique-middle-mode-ii.js)|Hard|
 3422|[Minimum Operations to Make Subarray Elements Equal](./solutions/3422-minimum-operations-to-make-subarray-elements-equal.js)|Medium|
 3423|[Maximum Difference Between Adjacent Elements in a Circular Array](./solutions/3423-maximum-difference-between-adjacent-elements-in-a-circular-array.js)|Easy|
+3431|[Minimum Unlocked Indices to Sort Nums](./solutions/3431-minimum-unlocked-indices-to-sort-nums.js)|Medium|
 3439|[Reschedule Meetings for Maximum Free Time I](./solutions/3439-reschedule-meetings-for-maximum-free-time-i.js)|Medium|
 3440|[Reschedule Meetings for Maximum Free Time II](./solutions/3440-reschedule-meetings-for-maximum-free-time-ii.js)|Medium|
 3442|[Maximum Difference Between Even and Odd Frequency I](./solutions/3442-maximum-difference-between-even-and-odd-frequency-i.js)|Easy|
diff --git a/solutions/3431-minimum-unlocked-indices-to-sort-nums.js b/solutions/3431-minimum-unlocked-indices-to-sort-nums.js
@@ -0,0 +1,44 @@
+/**
+ * 3431. Minimum Unlocked Indices to Sort Nums
+ * https://leetcode.com/problems/minimum-unlocked-indices-to-sort-nums/
+ * Difficulty: Medium
+ *
+ * You are given an array nums consisting of integers between 1 and 3, and a binary array
+ * locked of the same size.
+ *
+ * We consider nums sortable if it can be sorted using adjacent swaps, where a swap between
+ * two indices i and i + 1 is allowed if nums[i] - nums[i + 1] == 1 and locked[i] == 0.
+ *
+ * In one operation, you can unlock any index i by setting locked[i] to 0.
+ *
+ * Return the minimum number of operations needed to make nums sortable. If it is not possible
+ * to make nums sortable, return -1.
+ */
+
+/**
+ * @param {number[]} nums
+ * @param {number[]} locked
+ * @return {number}
+ */
+var minUnlockedIndices = function(nums, locked) {
+  let currentMax = 1;
+  let locks = 0;
+  let result = 0;
+
+  for (let i = 0; i < nums.length; i++) {
+    if (currentMax < nums[i]) {
+      currentMax = nums[i];
+      locks = 0;
+    }
+    if (nums[i] < currentMax) {
+      if (nums[i] + 1 < currentMax) {
+        return -1;
+      }
+      result += locks;
+      locks = 0;
+    }
+    locks += locked[i];
+  }
+
+  return result;
+};
