等差数列
求1+2+3+...+n
http://www.nowcoder.com/questionTerminal/7a0da8fc483247ff8800059e12d7caf1
class Solution { public: int Sum_Solution(int n) { double a = n; a = ((1.0 + a) / 2) * a; return (int)a; } };
求1+2+3+...+n
http://www.nowcoder.com/questionTerminal/7a0da8fc483247ff8800059e12d7caf1
class Solution { public: int Sum_Solution(int n) { double a = n; a = ((1.0 + a) / 2) * a; return (int)a; } };
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