题解 | #求1+2+3+...+n#
求1+2+3+...+n
http://www.nowcoder.com/practice/7a0da8fc483247ff8800059e12d7caf1
public class Solution { public int Sum_Solution(int n) { return (n + fun(n,n)) >> 1; //把这道题带入等差数列的公式即可 }
public int fun(int n1,int n2) {//用加法求n^2
if(n2 == 1) return n1;
return n1 + fun(n1,--n2);
}
}
查看12道真题和解析