剑指offer 31. 时间效率 整数中1出现的次数（从1到n整数中1出现的次数）

 public int NumberOf1Between1AndN_Solution(int n) {
        int count=0;
        for (int i = 1; i <=n; i++) {
            String numString=String.valueOf(i);
            while (numString.indexOf("1")>=0) {
                numString=numString.substring(numString.indexOf("1")+1);
                count++;
            }
        } 
         return count;  
        }