Added soltion for max sum of numbers with equal sum digit.

anxious-coder-lhs · anxious-coder-lhs · commit a34f34717c1d · 2020-11-12T12:32:54.000+05:30
diff --git a/README.md b/README.md
@@ -58,6 +58,7 @@ Happy to accept any contributions to this in any langugage.
 23. [Leet Code 59 - Spiral Matrix II](https://leetcode.com/problems/spiral-matrix-ii/) | [Solution](level_medium/SpiralMatrixII.ts)
 24. [Leet Code 151 - Reverse Words in a String](https://leetcode.com/problems/reverse-words-in-a-string/) | [Solution](level_medium/LeetCode_151_Reverse_Words_In_a_String.ts)
 25. [Leet Code 1647 - Minimum Deletions to Make Character Frequency Unique](https://leetcode.com/problems/minimum-deletions-to-make-character-frequencies-unique/) | [Solution](level_medium/LeetCode_1647_Min_Deletions_For_Unique_Freq.ts)
+26. [Microsoft OA - Max Sum of Numbers with Equal Sum Digits](https://leetcode.com/discuss/interview-question/915683/) | [Solution](./level_medium/MaxSumOfNumbersWithEqualSumOfDigit.ts)
 
 
 ## Hard
diff --git a/level_medium/MaxSumOfNumbersWithEqualSumOfDigit.ts b/level_medium/MaxSumOfNumbersWithEqualSumOfDigit.ts
@@ -0,0 +1,47 @@
+import { S_IFDIR } from "constants";
+import { diffieHellman } from "crypto";
+
+/**
+ * Problem: https://leetcode.com/discuss/interview-question/915683/
+ * 
+ * Solution is based on the hashing technique. For any element which has the same digit sum, we can hash it by digit sum
+ * and save it. Once we have any item saved, we can compamake all possible pairs of it and calculate the maximum sum.
+ * 
+ * However, creating every pair is O(n*n), which can be optimized, by only keeping track of the max element so far.
+ * If the new element, creates a sum which is max than the earlier, we know the new curr is maximum of all the previously
+ * seen.
+ * 
+ * Time: O(n), Space: O(n) for hashing.
+ */
+function findMaxSum(input: number[]): number {
+    // Will keep track of the max element for each pair of the digit sum that we find.
+    const map = new Map<number, number>();
+    let max = -Infinity;
+    input.forEach(curr => {
+        const digitSum = getDigitSum(curr)
+        if (map.has(digitSum)) {
+            const prev = map.get(digitSum)
+            max = Math.max(max, prev + curr)
+            // Update the previous stored element for digit sum if this is greater.
+            map.set(digitSum, Math.max(prev, curr));
+        } else {
+            map.set(digitSum, curr);
+        }
+    });
+
+    return max !== -Infinity ? max : -1;
+}
+
+function getDigitSum(elem) {
+    let sum = 0;
+    while(elem !== 0) {
+        sum += elem % 10;
+        elem = Math.floor(elem / 10)
+    }
+
+    return sum
+}
+
+console.log(findMaxSum([51, 71, 17, 42]))
+console.log(findMaxSum([42, 33, 60]))
+console.log(findMaxSum([51, 32, 43]))
