problem1 link 这个可以贪心地从前向后构造.假设当前已经的字符串为$S$,对于一个字符$c$来说,设将$c$加到$S$后得到的新串为$S^{'}$.那么如果$X+Y+Z \ge minInv$,那么这个之后的构造就是有解的.其中$X$表示$S^{'}$中逆序对个数:$Y$表示剩下的字符与$S^{'}$中的字符构成的逆序对的个数:$Z$表示剩下的字符能构成的最大逆序对个数(从大到小排列即可). problem2 link 首先处理掉垂直发射的情况.剩下的就是不垂直的.直接枚举直线的斜率…
problem1 link 倒着想.每次添加一个右括号再添加一个左括号,直到还原.那么每次的右括号的选择范围为当前左括号后面的右括号减去后面已经使用的右括号. problem2 link 令$h(x)=\sum_{i=1}^{x}g(i)$,那么答案为$h(R)-h(L-1)$.对于$h(x)$: (1)如果$x\leq K$,那么$h(x)=0$ (2)否则对于$[K+1,x]$之间的所有偶数来说,对答案的贡献为$even+h(\frac{x}{2})-h(\frac{K}{2})$,其中$e…
Problem Statement You are given the ints perimeter and area. Your task is to find a triangle with the following properties: The coordinates of each vertex are integers between 0 and 3000, inclusive. The perimeter of the triangle must be exactly…
Problem Statement The Happy Letter game is played as follows: At the beginning, several players enter the field. Each player has a lowercase English letter on their back. The game is played in turns. In each turn, you select two players with dif…
