1295. Find Numbers with Even Number of Digits

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Array

Time: O(n)

Space: O(1)

Intuition

Count numbers with an even number of digits. Check digit count of each number.

Algorithm

1For each num: count digits (or check if in range 10-99, 1000-9999, etc.).
2Count those with even digit length.

Common Pitfalls

•Simple digit count. Numbers 10-99 (2 digits), 1000-9999 (4 digits), 100000-999999 (6 digits) have even digits.

1295.cs

// Approach: Count numbers that fall in the even-digit ranges (10-99, 1000-9999, 100000).
// Time: O(n) Space: O(1)

public class Solution
{
    public int FindNumbers(int[] nums)
    {
        int ans = 0;

        foreach (int num in nums)
        {
            if ((num > 9 && num < 100) || (num > 999 && num < 10000) || num == 100000)
                ans++;
        }

        return ans;
    }
}

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