180th Commit

README.md

@@ -122,9 +122,10 @@ Ace Coding Interview with 75 Qs
 | Prefix Sum                      |                  |      |
 | ------------------------------- | ---------------- | ---- |
 | 1732. Find the Highest Altitude | [Solution][1732] | Easy |
-| 724. Find Pivot Index           | Solution         | Easy |
+| 724. Find Pivot Index           | [Solution][724]  | Easy |
 
 [1732]: ./src/page-16/1732.%20Find%20the%20Highest%20Altitude/largestAltitude.ts
+[724]: ./src/page-7/724.%20Find%20Pivot%20Index/pivotIndex.ts
 
 | Hash Map / Set                           |          |        |
 | ---------------------------------------- | -------- | ------ |

src/page-7/724. Find Pivot Index/pivotIndex.test.ts

@@ -0,0 +1,9 @@
+import { pivotIndex } from './pivotIndex';
+
+describe('724. Find Pivot Index', () => {
+  test('pivotIndex', () => {
+    expect(pivotIndex([1, 7, 3, 6, 5, 6])).toBe(3);
+    expect(pivotIndex([1, 2, 3])).toBe(-1);
+    expect(pivotIndex([2, 1, -1])).toBe(0);
+  });
+});

src/page-7/724. Find Pivot Index/pivotIndex.ts

@@ -0,0 +1,23 @@
+type PivotIndex = (nums: number[]) => number;
+
+/**
+ * Accepted
+ */
+export const pivotIndex: PivotIndex = (nums) => {
+  // Calculate the total sum of the array
+  const totalSum = nums.reduce((acc, num) => acc + num, 0);
+
+  // Initialize the left sum as 0
+  let leftSum = 0;
+
+  for (let i = 0; i < nums.length; i++) {
+    // Check if the left sum is equal to the right sum
+    if (leftSum === totalSum - leftSum - nums[i]) return i;
+
+    // Update the left sum by adding the current element
+    leftSum += nums[i];
+  }
+
+  // If no pivot index is found, return -1
+  return -1;
+};