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Find Lucky Integer in an Array - Easy - LeetCode - MiniTV

Find Lucky Integer in an Array - Easy - LeetCode - मिनी टीवी

Given an array of integers arr, a lucky integer is an integer which has a frequency in the array equal to its value.

Return a lucky integer in the array. If there are multiple lucky integers return the largest of them. If there is no lucky integer return -1.

 

Example 1:

Input: arr = [2,2,3,4]

Output: 2

Explanation: The only lucky number in the array is 2 because frequency[2] == 2.

 

Example 2:

Input: arr = [1,2,2,3,3,3]

Output: 3

Explanation: 1, 2, and 3 are all lucky numbers, return the largest of them.

 

Example 3:

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

Output: -1

Explanation: There are no lucky numbers in the array.

 

Example 4:

Input: arr = [5]

Output: -1

 

Example 5:

Input: arr = [7,7,7,7,7,7,7]

Output: 7

 

 

Constraints:

1 <= arr.length <= 500

1 <= arr[i] <= 500

 

Solution:

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

namespace LeetCode.AskGif.Easy.Array
{
    public class FindLuckySoln
    {
        public int FindLucky(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);
                }
            }

            int max = -1;
            foreach (var item in map)
            {
                if(item.Key == item.Value && item.Key > max)
                {
                    max = item.Key;
                }
            }

            return max;
        }
    }
}

 

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 FindLuckySolnTests
    {
        [TestMethod]
        public void FindLuckySoln_First()
        {
            var arr = new int[] { 2, 2, 3, 4 };
            var output = 2;
            var res = new FindLuckySoln().FindLucky(arr);

            Assert.AreEqual(res, output);
        }

        [TestMethod]
        public void FindLuckySoln_Second()
        {
            var arr = new int[] { 1, 2, 2, 3, 3, 3 };
            var output = 3;
            var res = new FindLuckySoln().FindLucky(arr);

            Assert.AreEqual(res, output);
        }

        [TestMethod]
        public void FindLuckySoln_Third()
        {
            var arr = new int[] { 2, 2, 2, 3, 3 };
            var output = -1;
            var res = new FindLuckySoln().FindLucky(arr);

            Assert.AreEqual(res, output);
        }

        [TestMethod]
        public void FindLuckySoln_Fourth()
        {
            var arr = new int[] { 5 };
            var output = -1;
            var res = new FindLuckySoln().FindLucky(arr);

            Assert.AreEqual(res, output);
        }

        [TestMethod]
        public void FindLuckySoln_Fifth()
        {
            var arr = new int[] { 7, 7, 7, 7, 7, 7, 7 };
            var output = 7;
            var res = new FindLuckySoln().FindLucky(arr);

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