Add two missing nums problem

Author: sudheerj

src/java1/algorithms/array/twoMissingNumbers/TwoMissingNumbers.java

@@ -0,0 +1,66 @@
+package twoMissingNumbers;
+
+import java.util.Arrays;
+
+public class TwoMissingNumbers {
+
+    //TC: O(n) SC: O(n)
+    private static int[] findTwoMissingNumbers(int[] nums) {
+        boolean[] present = new boolean[nums.length + 2];
+        int[] missingNums = new int[2];
+
+        for(int num: nums) {
+            present[num-1] = true;
+        }
+
+        int j=0;
+        for(int i=1; i<= nums.length+2; i++){
+            if(!present[i-1]) {
+                missingNums[j++] = i;
+            }
+        }
+
+        return missingNums;
+    }
+
+    //TC: O(n) SC: O(1)
+    private static int[] findTwoMissingNumbers1(int[] nums) {
+        int[] missingTwoNums = new int[2];
+        int len = nums.length + 2;
+        int sum = (len * (len + 1))/2;
+        int numsSum = 0;
+
+        for (int num : nums) {
+            numsSum += num;
+        }
+
+        int missingTwoNumsSum = sum - numsSum;
+        int missingTwoNumsAvg = missingTwoNumsSum/2;
+
+        int sumUntilAvg = missingTwoNumsAvg * (missingTwoNumsAvg + 1)/2;
+        int sumUntilNumsAvg = 0;
+
+        for (int i = 0; i < nums.length; i++) {
+            if(nums[i] <= missingTwoNumsAvg) {
+                sumUntilNumsAvg += nums[i];
+            }
+        }
+
+        int firstMissingNum = sumUntilAvg - sumUntilNumsAvg;
+        missingTwoNums[0] = firstMissingNum;
+        missingTwoNums[1] = missingTwoNumsSum - firstMissingNum;
+
+        return missingTwoNums;
+    }
+
+    public static void main(String[] args) {
+        int[] nums1 = {3, 2, 5, 1, 6, 8};
+        int[] nums2 = {3, 2, 5, 1, 6, 4};
+
+        System.out.println(Arrays.toString(findTwoMissingNumbers(nums1)));
+        System.out.println(Arrays.toString(findTwoMissingNumbers(nums2)));
+
+        System.out.println(Arrays.toString(findTwoMissingNumbers1(nums1)));
+        System.out.println(Arrays.toString(findTwoMissingNumbers1(nums2)));
+    }
+}

src/javascript/algorithms/array/twoMissingNumbers/twoMissingNumbers.js

@@ -0,0 +1,56 @@
+//TC: O(n) SC: O(n)
+function findTwoMissingNumbers(nums) {
+    let present = new Array(nums.length+2).fill(false);
+    let missingTwoNums = [];
+
+    for(let num of nums) {
+        present[num-1] = true;
+    }
+
+    for (let i = 1; i <= nums.length+2; i++) {
+        if(!present[i-1]) {
+            missingTwoNums.push(i);
+        }
+    }
+
+    return missingTwoNums;
+}
+
+//TC: O(n) SC: O(1)
+function findTwoMissingNumbers1(nums) {
+    let missingTwoNums =[];
+    let len = nums.length+2;
+    let sum = Math.floor((len * (len + 1))/2);
+
+    let numsSum = 0;
+    for (let i = 0; i < nums.length; i++) {
+        numsSum += nums[i];
+    }
+
+    let missingTwoNumsSum = sum - numsSum; 
+    let missingTwoNumsAvg = Math.floor(missingTwoNumsSum/2); 
+
+    let sumUntilAvg = Math.floor((missingTwoNumsAvg * (missingTwoNumsAvg + 1))/2); 
+    let numsSumUntilAvg = 0;
+    
+    for(let i=0; i<nums.length; i++){
+        if(nums[i] <= missingTwoNumsAvg) {
+            numsSumUntilAvg += nums[i]; 
+        }
+    }
+
+    let missingFirstNum = sumUntilAvg-numsSumUntilAvg;
+    missingTwoNums.push(missingFirstNum);
+    missingTwoNums.push(missingTwoNumsSum - missingFirstNum);
+    
+    return missingTwoNums;
+}
+
+
+const nums1 = [3, 2, 5, 1, 6, 8];
+const nums2 = [3, 2, 5, 1, 6, 4];
+console.log(findTwoMissingNumbers(nums1));
+console.log(findTwoMissingNumbers(nums2));
+
+console.log(findTwoMissingNumbers1(nums1));
+console.log(findTwoMissingNumbers1(nums2));