QTREE - Query on a tree
You are given a tree (an acyclic undirected connected graph) with N nodes, and edges numbered 1, 2, 3...N-1.
We will ask you to perfrom some instructions of the following form:
- CHANGE i ti : change the cost of the i-th edge to ti
- QUERY a b : ask for the maximum edge cost on the path from node a to node b
The first line of input contains an integer t, the number of test cases (t <= 20). t test cases follow.
For each test case:
- In the first line there is an integer N (N <= 10000),
- In the next N-1 lines, the i-th line describes the i-th edge: a line with three integers a b c denotes an edge between a, b of cost c (c <= 1000000),
- The next lines contain instructions "CHANGE i ti" or "QUERY a b",
- The end of each test case is signified by the string "DONE".
There is one blank line between successive tests.
For each "QUERY" operation, write one integer representing its result.
Input: 1 3 1 2 1 2 3 2 QUERY 1 2 CHANGE 1 3 QUERY 1 2 DONE Output: 1 3
Last edit: 2021-03-11 15:22:43
best place to study heavy light decompostion
Not kidding. What's HLD? Please tell me...Last edit: 2020-08-30 16:17:01
Nice problem to learn HLD :)
If you are getting RE SIGSEGV, use void return type with functions not returning anything.
There's no need to find LCA separately if you are using HLD.
I add ios_base::sync_with_stdio(false);cin.tie(NULL); and TLE becomes AC
getting tle on cpp is that ok
See this as well.
if you get TLE, just optimize function max, dfs & hld decomposition like this guy : https://ideone.com/Ykg63S
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