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codeforce-1092-F. Tree with Maximum Cost-树上换根【Description】You are given a tree consisting exactly of n vertices. Tree is a connected undirectedgraph with n−1 edges. Each vertex v of this tree has a...

codeforce-1092-E. Minimal Diameter Forest-树的直径与合并【Description】You are given a forest — an undirected graph with n vertices such that each its connected component is a tree.The diameter (aka "long...

Codeforce-1059-E. Split the Tree-树上倍增【Description】You are given a rooted tree on n vertices, its root is the vertex number 1. The i-th vertex contains a number wi. Split it into the minimum possibl...

Codeforces Round #532 (Div. 2)-E. Andrew and Taxi-二分+拓扑排序【Description】Andrew prefers taxi to other means of transport, but recently most taxi drivers have been acting inappropriately. In order to e...

Codeforces Round #544 (Div. 3)-F2. Spanning Tree with One Fixed Degree-求无向图中满足1号节点的度为d的生成树【Description】You are given an undirected unweighted connected graph consisting of n vertices and m edges. I...

图论-最短路个人总结差分约束如若一个系统由n个变量和m个不等式组成，并且这m个不等式对应的系数矩阵中每一行有且仅有一个1和-1，其它的都为0，这样的系统称为差分约束( difference constraints )系统对于形如：B−A<=c⋯(1)C−B<=a⋯(2)C−A<=b⋯(3)对于形如：\\B-A<=c\cdots (1...