Open huoxiangdong opened 6 years ago
1 10 2 9 3 8 4 7 5 6 --> (1+10) x (10/2) --> 10x(1+10)/2 --> (n+1)xn/2
1 10 2 9 3 8 4 7 5 6 --> (1+10) x (10/2) --> 10x(1+10)/2 --> (n+1)xn/2