题解 | #求1+2+3+...+n#
求1+2+3+...+n
http://www.nowcoder.com/practice/7a0da8fc483247ff8800059e12d7caf1
1 python解法：幂运算加位运算
# -*- coding:utf-8 -*- class Solution: def Sum_Solution(self, n): # write code here return ((n**2-n)>>1)+n
2.java解法：也是幂运算加位运算，但是没有python 简洁
public class Solution {
public int Sum_Solution(int n) {
return ((((new Double(Math.pow(n,2))).intValue())-n)>>1)+n;
//return (int((Math.pow(n, 2)-n))>>2)+n;
}
} 