Partition Array Into Three Parts With Equal Sum - Easy - LeetCode

Given an array A of integers, return true if and only if we can partition the array into three non-empty parts with equal sums.

Formally, we can partition the array if we can find indexes i+1 < j with (A[0] + A[1] + ... + A[i] == A[i+1] + A[i+2] + ... + A[j-1] == A[j] + A[j-1] + ... + A[A.length - 1])

Example 1:

Input: A = [0,2,1,-6,6,-7,9,1,2,0,1]

Output: true

Explanation: 0 + 2 + 1 = -6 + 6 - 7 + 9 + 1 = 2 + 0 + 1

Example 2:

Input: A = [0,2,1,-6,6,7,9,-1,2,0,1]

Output: false

Example 3:

Input: A = [3,3,6,5,-2,2,5,1,-9,4]

Output: true

Explanation: 3 + 3 = 6 = 5 - 2 + 2 + 5 + 1 - 9 + 4

Constraints:

3 <= A.length <= 50000

-10^4 <= A[i] <= 10^4

Solution:

using System;
using System.Collections.Generic;
using System.Text;

namespace LeetCode.AskGif.Easy.Array
{
 public class CanThreePartsEqualSumSoln
 {
 public bool CanThreePartsEqualSum(int[] A)
 {
 var sum = 0;
 for (int i = 0; i < A.Length; i++)
 {
 sum += A[i];
 }

 if(sum%3 != 0)
 {
 return false;
 }

 int parts = sum / 3;
 int partsCount = 0;

 int temp = 0;
 for (int i = 0; i < A.Length; i++)
 {
 temp += A[i];
 if(temp == parts)
 {
 temp = 0;
 partsCount++;
 }
 }

 return temp == 0 && partsCount >= 3;
 }
 }
}

Time Complexity: O(n)

Space Complexity: O(1)

Unit Tests:

using LeetCode.AskGif.Easy.Array;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System;
using System.Collections.Generic;
using System.Text;

namespace CodingUnitTest.Easy.Array
{
 [TestClass]
 public class CanThreePartsEqualSumSolnTests
 {
 [TestMethod]
 public void CanThreePartsEqualSumSoln_First()
 {
 var arr = new int[] { 0, 2, 1, -6, 6, -7, 9, 1, 2, 0, 1 };
 var expected = true;

 var res = new CanThreePartsEqualSumSoln().CanThreePartsEqualSum(arr);
 Assert.AreEqual(expected, res);
 }

 [TestMethod]
 public void CanThreePartsEqualSumSoln_Second()
 {
 var arr = new int[] { 0, 2, 1, -6, 6, 7, 9, -1, 2, 0, 1 };
 var expected = false;

 var res = new CanThreePartsEqualSumSoln().CanThreePartsEqualSum(arr);
 Assert.AreEqual(expected, res);
 }

 [TestMethod]
 public void CanThreePartsEqualSumSoln_Third()
 {
 var arr = new int[] { 3, 3, 6, 5, -2, 2, 5, 1, -9, 4 };
 var expected = true;

 var res = new CanThreePartsEqualSumSoln().CanThreePartsEqualSum(arr);
 Assert.AreEqual(expected, res);
 }

 [TestMethod]
 public void CanThreePartsEqualSumSoln_Fourth()
 {
 var arr = new int[] { 1, -1, 1, -1 };
 var expected = false;

 var res = new CanThreePartsEqualSumSoln().CanThreePartsEqualSum(arr);
 Assert.AreEqual(expected, res);
 }

 [TestMethod]
 public void CanThreePartsEqualSumSoln_Fifth()
 {
 var arr = new int[] { 10, -10, 10, -10, 10, -10, 10, -10 };
 var expected = true;

 var res = new CanThreePartsEqualSumSoln().CanThreePartsEqualSum(arr);
 Assert.AreEqual(expected, res);
 }
 }
}