Description A young schoolboy would like to calculate the sum for some fixed natural k and different natural n. He observed that calculating ik for all i (1<=i<=n) and summing up results is a too slow way to do it, because the number of required ari…
Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number. An example is the root-to-leaf path 1->2->3 which represents the number 123. Find the total sum of all root-to-leaf numbers. For example, 1 / \ 2 3…
问题描述: Calculate the sum of two integers a and b, but you are not allowed to use the operator + and -. Example: Given a = 1 and b = 2, return 3. 问题分析: 首先我们可以分析人们是如何做十进制的加法的,比如是如何得出5+17=22这个结果的.实际上,我们可以分成三步的:第一步只做各位相加不进位,此时相加的结果是12(个位数5和7相加不要进位是2,十位数0和…