Sheila is a student and she drives a typical student car: it is old, slow, rusty, and falling apart. Recently, the needle on the speedometer fell off. She glued it back on, but she might have placed it at the wrong angle. Thus, when the speedometer r…
Preorder Test 题目连接: http://www.codeforces.com/contest/627/problem/D Description For his computer science class, Jacob builds a model tree with sticks and balls containing n nodes in the shape of a tree. Jacob has spent ai minutes building the i-th ba…
D. Dense Subsequence time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output You are given a string s, consisting of lowercase English letters, and the integer m. One should choose some symbols fr…