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Check If N and Its Double Exist - Array - Easy - LeetCode - MiniTV

Check If N and Its Double Exist - Array - Easy - LeetCode - मिनी टीवी

Given an array arr of integers, check if there exist two integers N and M such that N is the double of M ( i.e. N = 2 * M).

More formally check if there exists two indices i and j such that :

i != j

0 <= i, j < arr.length

arr[i] == 2 * arr[j]

 

Example 1:

Input: arr = [10,2,5,3]

Output: true

Explanation: N = 10 is the double of M = 5,that is, 10 = 2 * 5.

 

Example 2:

Input: arr = [7,1,14,11]

Output: true

Explanation: N = 14 is the double of M = 7,that is, 14 = 2 * 7.

 

Example 3:

Input: arr = [3,1,7,11]

Output: false

Explanation: In this case does not exist N and M, such that N = 2 * M.

 

Constraints:

2 <= arr.length <= 500

-10^3 <= arr[i] <= 10^3

 

Solution:

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

namespace LeetCode.AskGif.Easy.Array
{
    public class CheckIfExistSoln
    {
        public bool CheckIfExist(int[] arr)
        {
            var map = new Dictionary<int, int>();
            for (int i = 0; i < arr.Length; i++)
            {
                if (map.ContainsKey(arr[i]))
                {
                    map[arr[i]]++;
                }
                else
                {
                    map.Add(arr[i], 1);
                }
            }

            if (map.ContainsKey(0) && map[0] == 2)
            {
                return true;
            }

            map.Remove(0);

            for (int i = 0; i < arr.Length; i++)
            {
                if(map.ContainsKey(arr[i] * 2))
                {
                    return true;
                }
            }

            return false;
        }
    }
}

 

Time Complexity: O(n)

Space Complexity: O(n)

 

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 CheckIfExistSolnTests
    {
        [TestMethod]
        public void CheckIfExistSoln_First()
        {
            var arr = new int[] { 10, 2, 5, 3 };
            var output = true;
            var res = new CheckIfExistSoln().CheckIfExist(arr);

            Assert.AreEqual(res, output);
        }

        [TestMethod]
        public void CheckIfExistSoln_Second()
        {
            var arr = new int[] { 7, 1, 14, 11 };
            var output = true;
            var res = new CheckIfExistSoln().CheckIfExist(arr);

            Assert.AreEqual(res, output);
        }

        [TestMethod]
        public void CheckIfExistSoln_Third()
        {
            var arr = new int[] { 3, 1, 7, 11 };
            var output = false;
            var res = new CheckIfExistSoln().CheckIfExist(arr);

            Assert.AreEqual(res, output);
        }

        [TestMethod]
        public void CheckIfExistSoln_Fourth()
        {
            var arr = new int[] { -2, 0, 10, -19, 4, 6, -8 };
            var output = false;
            var res = new CheckIfExistSoln().CheckIfExist(arr);

            Assert.AreEqual(res, output);
        }
    }
}