Merge pull request #2560 from aadil42/patch-52

Create 0041-first-missing-positive.js

javascript/0041-first-missing-positive.js

@@ -0,0 +1,56 @@
+/**
+ * Cyclic Sort
+ * Time O(N) | Space O(1)
+ * https://leetcode.com/problems/first-missing-positive
+ * @param {number[]} nums
+ * @return {number}
+ */
+var firstMissingPositive = (nums) => {
+  cyclicSort(nums);
+
+  return search(nums);
+};
+
+const cyclicSort = (nums, index = 0) => {
+  while (index < nums.length) {
+    const num = nums[index];
+    const indexKey = (num - 1);
+    const indexNum = nums[indexKey];
+
+    if (canSwap(nums, num, indexNum)) {
+      swap(nums, index, indexKey);
+      continue;
+    }
+
+    index += 1;
+  }
+}
+
+const search = (nums, index = 0) => {
+  while (index < nums.length) {
+    const num = nums[index];
+    const indexKey = (index + 1);
+
+    if (!isEqual(num, indexKey)) return indexKey;
+
+    index += 1;
+  }
+
+  return (nums.length + 1);
+}
+
+const canSwap = (nums, num, indexNum) =>
+  isPositive(num) &&
+  isInBound(num, nums) &&
+  !isEqual(num, indexNum);
+
+const swap = (nums, index, indexKey) => 
+  [nums[index], nums[indexKey]] = [nums[indexKey], nums[index]];
+
+const isPositive = (num) => (0 < num);
+
+const isInBound = (num, nums) => (num <= nums.length);
+
+const isEqual = (num, indexNum) => (num === indexNum);
+
+