JZ31 整数中1出现的次数（从1到n整数中1出现的次数)

过了就行吧，
优化还没看

import java.util.*;
public class Solution {
    public int NumberOf1Between1AndN_Solution(int n) {
        int res = 0;
        for(int i=1; i<= n; i++){
            String temp = String.valueOf(i);
            for(char c : temp.toCharArray()){
                if(c=='1') res++;
            }
        }
        return res;
    }
}