2020-2021:teams:hotpot:2020nowcoder5
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2020-2021:teams:hotpot:2020nowcoder5 [2020/07/31 11:51] misakatao 更新 |
2020-2021:teams:hotpot:2020nowcoder5 [2020/07/31 16:29] (当前版本) 喝西北风 |
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| 行 19: | 行 19: | ||
| ===题解=== | ===题解=== | ||
| - | ====B - ==== | + | ====B - Graph==== |
| - | ===solved by === | + | ===solved by gyp,tyx=== |
| ===题意=== | ===题意=== | ||
| + | |||
| + | 给定一棵树。每次可以添加一条边或删去一条边。保证任何时候一定是连通图，每个环上的边异或和为0。求所有边的和最小是多少 | ||
| ===数据范围=== | ===数据范围=== | ||
| + | |||
| + | $2\le n \le 10^5$,$0 \le w < 2^30$ | ||
| ===题解=== | ===题解=== | ||
| - | ====C - ==== | + | 可以证明，每条边的长度是确定的。任取一点为根，可以计算出每一点到根的所有边的异或和，记为$a_i$。本题等价于求一个最小生成树，第i和第j个点的边权为$a_i \bigoplus a_j$。先按升序排序。从最高位开始，从所有最高位是1和最高位是0的里各选一个数，使得其异或结果最小，这条边被计入。然后再分别从两个部分再进行类似的操作。 |
| - | ===solved by === | + | ====C - Easy==== |
| + | |||
| + | ===upsolved by gyp=== | ||
| ===题意=== | ===题意=== | ||
| + | |||
| + | 给定n,m,k。对长度为k的正整数序列$\sum_{i=1}^k a_i=n$,$\sum_{i=1}^k b_i=m$，$P=\prod_{i=1}^kmin(a_i,b_i)$。求所有满足要求的a,b对应的P的和 | ||
| ===数据范围=== | ===数据范围=== | ||
| + | |||
| + | $T\le 100$,$1\le n,m\le 10^6,1\le k\le min(n,m)$ | ||
| ===题解=== | ===题解=== | ||
| + | |||
| + | 对于给定的a,b，P为满足$c_i\le min(a_i,b_i)$，长度为k的正整数序列c的个数。对于任意c，设$S=\sum_{i=1}^kc_i$，一共有$C_{n-S+k-1}^{k-1}\cdot C_{m-S+k-1}^{k-1}$个a,b包含c。枚举S即可。 | ||
| ====D - ==== | ====D - ==== | ||
| 行 101: | 行 113: | ||
| ===题解=== | ===题解=== | ||
| - | ====I - ==== | + | ====I - Hard Math Problem==== |
| - | ===solved by === | + | ===solved by gyp=== |
| ===题意=== | ===题意=== | ||
| + | |||
| + | 很奇怪的一道数学题，没有输入，只输出一个结果 | ||
| ===数据范围=== | ===数据范围=== | ||
| + | |||
| + | 无 | ||
| ===题解=== | ===题解=== | ||
| + | |||
| + | 反正答案是2/3。试也能试出来，并不会证。 | ||
| ====J - ==== | ====J - ==== | ||
2020-2021/teams/hotpot/2020nowcoder5.1596167477.txt.gz · 最后更改: 2020/07/31 11:51 由 misakatao
