Today I have done leetcode's July LeetCoding Challenge with cpp.

July LeetCoding Challenge 5

Description

Find Lucky Integer in an Array

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

Return the largest lucky integer in the array. 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.

Constraints:

• 1 <= arr.length <= 500
• 1 <= arr[i] <= 500

Solution

class Solution {
public:
  int findLucky(vector<int>& arr) {
    map<int, int> count;
    for(auto n : arr) count[n] += 1;
    int answer = -1;
    for(auto [n, c] : count) {
      if(n == c) answer = n;
    }
    return answer;
  }
};

// Accepted
// 101/101 cases passed (0 ms)
// Your runtime beats 100 % of cpp submissions
// Your memory usage beats 37.37 % of cpp submissions (13.9 MB)