Find Lucky Integer in an Array Leetcode Solution

Problem statement

In the problem " Find Lucky Integer in an Array " we are given an array where an integer is called lucky if its frequency in the array is equal to its value.

 

Our task is to return the largest lucky number. If no such number exists we have to return -1. Values in the array lie between 1 and 500 and the length of the array is a maximum of 500.

Example

arr =

2

Explanation:

 

The frequency of 2 is 2 and the frequency of 3 and four is 1. As 2 is the only lucky integer so this is our answer.

Sorting Approach for Find Lucky Integer in an Array Leetcode Solution

As we want to count the number of occurrences of each number and then find the greatest element satisfying the given condition. To do this we will pick a number and then traverse the entire array to count its occurrences and then select the greatest element satisfying the condition. Here we need to traverse the complete array n times so the time complexity becomes O(n*n). We can increase the performance by sorting the array. This will bring the same numbers together. We will follow these steps:

 

- Sort the array in decreasing order.

- Count all occurrences of the encountered element if it satisfies the condition then return it.

- In the end, if no element satisfies the condition then return -1.

 

Implementation

C++ code for Find Lucky Integer in an Array

#includ

 

www.tutorialcup.com/leetcode-solutions/find-lucky-integer...

Done