# Blogs Hub

### by Sumit Chourasia | Jun 06, 2020 | Category :coding | Tags : आसानc-sharpleetcodearrayalgorithmडेटा-संरचना

#### 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;

{
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
{
}
}

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);
}
}
}
``````

Contributed By: Sumit Chourasia
Contributed By: Sumit Chourasia
Contributed By: Sumit Chourasia
Contributed By: Sumit Chourasia