Given an array of integers, every element appears twice except for one. Find that single one. 大意为给定一个整数数组，数组中除了一个元素只有一个外

Given a non negative integer number num. For every numbers i in the range 0 ≤ i ≤ num calculate the number of 1’s in the

异或为相同为 0 相异为 1 例子 010101 ^ 001011 = 011110 规则 a ^ a = 0 ------>幂 a ^ b = b ^ a ------>交换 a ^ 0 = a ------>与0异或 a

给定一个正整数数组，找出所有可以相加得到目标正整数的组合 Example: 给定数组:{1,2,3} 目标数:4 可能情况: {1,1,1,1} {1,1,2},