problem1 link $f[i][j]$表示经过前$i$个怪物之后,花费$j$个硬币可以得到的最大值. problem2 link 设$nim[i]$表示数字$i$的nim值.那么题目就是求有多少个区间$[L,R]$满足这个区间内所有数字的nim值的抑或不是0．通过记录前缀和的个数,可以$O(n)$计算得到.现在问题是计算每个值的nim值. 可以用数学归纳法证明$i$的nim值等于$i$中的质因子的个数,比如$nim[6]=2,nim[12]=3$等.所以对于给出的的区间$[L,R]$,只…
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…
