题目链接———— Dima’s got a staircase that consists of n stairs. The first stair is at height a1, the second one is at a2, the last one is at an (1 ≤ a1 ≤ a2 ≤ … ≤ an).
Dima decided to play with the staircase, so he is throwing rectangular…
传送门:http://codeforces.com/problemset/problem/272/C C. Dima and Staircase time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output Dimas got a staircase that consists of n stairs. The first …
题意: 解法: 设 等 差 数 列 为 [ l , r ] 设等差数列为[l,r] 设等差数列为[l,r] n ∗ ( a 1 a n ) 2 \frac{n*(a_{1}a_{n})}{2} 2n∗(a1an) ( r − l 1 ) ( l r ) 2 n \frac{(r-l1)(lr)}{2}n 2(r−l1)(lr)n ( r − l 1 ) ∗ ( l r ) 2 n…