【思路】用&&的短路思想来求和
1 class Solution { 2 public: 3 int Sum_Solution(int n) { 4 int sum = n; 5 sum && (sum += Sum_Solution(n - 1)); 6 return sum; 7 } 8 };
[剑指Offer] 47.求1+2+3+...+n
原文：http://www.cnblogs.com/lca1826/p/6538621.html
