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## HDU 6023 ping ping ping

Time Limit: 2000/1000 MS (Java/Others) LCA + 贪心 The structure of the computer room in Northeastern University is pretty miraculous. There are $n$ servers, some servers connect to the gateway whose $IP$ address is $0$ directly. All servers are connected with each other by $n$ netting twines. It is said that this structure is favorable for maintaining physical problem of servers. （更多…）

## HDU 6121 Build a tree

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 524288/524288 K (Java/Others)

#### Problem Description

HazelFan wants to build a rooted tree. The tree has $n$ nodes labeled $0$ to $n−1$, and the father of the node labeled $i$ is the node labeled$$lfloor$frac{i-1}{k}\rfloor$. HazelFan wonders the size of every subtree, and you just need to tell him the $XOR$ value of these answers. （更多…）

## HDU 6044 Limited Permutation

##### Multi-University Training Team 1-1012虚建笛卡尔树
Time Limit: 4000/2000 MS (Java/Others) （更多…）

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## HDU 4034 Graph

Time Limit: 2000/1000 MS (Java/Others)

#### Problem Description

Everyone knows how to calculate the shortest path in a directed graph. In fact, the opposite problem is also easy. Given the length of shortest path between each pair of vertexes, can you find the original graph? （更多…）