1510. Find Lucky Integer In An Array¶

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1510. Find Lucky Integer in an Array

Easy

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(int[] arr) {
        int n = arr.length;
        int freq[] = new int[501];
        int maxi = -1;
        for (int ele : arr)
            freq[ele]++;
        for (int ele : arr)
            if (freq[ele] == ele)
                maxi = Math.max(maxi, ele);

        return maxi;
    }
}

Complexity Analysis¶

• Time Complexity: O(?)
• Space Complexity: O(?)

Approach¶

Detailed explanation of the approach will be added here