LeetCode/cs/count-symmetric-integers.cs

public class Solution {
    public int CountSymmetricIntegers(int low, int high) {
        var count = 0;

        for (var x = low; x <= high; ++x) {
            if (x < 100 && x % 11 == 0) {
                ++count;
            } else if (1000 <= x && x < 10000) {
                var left = x / 1000 + (x % 1000) / 100;
                var right = (x % 100) / 10 + x % 10;
                if (left == right) {
                    ++count;
                }
            }
        }

        return count;
    }
}