Count Integers With Even Digit Sum

给一个range[1,num], 求里面有多少数的digit sum是偶数.

class Solution {
    public int countEven(int num) {
        int res = 0;
        for(int i = 1; i <= num; i++){
            int even = 0;
            int cur = i;
            while(cur != 0){
                even += (cur  % 10);
                cur /= 10;
            }
            if(even % 2 == 0)
                res++;
        }
        return res;
    }
}