Merge pull request #1389 from loczek/41-First-Missing-Positive

Create: 41-First-Missing-Positive.ts

Author: Ahmad-A0

typescript/41-First-Missing-Positive.ts

@@ -0,0 +1,26 @@
+function firstMissingPositive(nums: number[]): number {
+    for (let i = 0; i < nums.length; i++) {
+        if (nums[i] < 0) {
+            nums[i] = 0;
+        }
+    }
+
+    for (let i = 0; i < nums.length; i++) {
+        let val = Math.abs(nums[i]);
+        if (1 <= val && val <= nums.length) {
+            if (nums[val - 1] > 0) {
+                nums[val - 1] *= -1;
+            } else if (nums[val - 1] === 0) {
+                nums[val - 1] = -1 * (nums.length + 1);
+            }
+        }
+    }
+
+    for (let i = 1; i < nums.length + 1; i++) {
+        if (nums[i - 1] >= 0) {
+            return i;
+        }
+    }
+
+    return nums.length + 1;
+}