problem1 link 设$f[i][j]$表示已经分配了answers中的前$i$个,分配给的问题的状态为 $j$的方案数. 其中状态可以用$n$位的三进制表示,0表示还未分配,1表示已分配是 Yes,2表示已分配是No. problem2 link 假设$n$个城市为[0,n-1].设$f[i][j][t]$表示在[0,i]个城市中已经选择了$j$个城市,选择了$t$个人的概率. 那么选择第$i+1$个城市的概率是$\frac{k-j}{n-i-1}$. problem3 link 首先…
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…
