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Apr 9, 2019 at 9:06pm
There is a field with plants — a grid with N rows (numbered 1 through N) and M columns (numbered 1 through M); out of its NM cells, K cells contain plants, while the rest contain weeds. Two cells are adjacent if they have a common side.
You want to build fences in the field in such a way that the following conditions hold for each cell that contains a plant:
it is possible to move from this cell to each adjacent cell containing a plant without crossing any fences
it is impossible to move from this cell to any cell containing weeds or to leave the grid without crossing any fences
The fences can only be built between cells or on the boundary of the grid, i.e. on the sides of cells. The total length of the built fences is the number of pairs of side-adjacent cells such that there is a fence built on their common side plus the number of sides of cells on the boundary of the grid which have fences built on them. Find the minimum required total length of fences that need to be built.
Input
The first line of the input contains a single integer T denoting the number of test cases. The description of T test cases follows.
The first line of each test case contains three space-separated integers N, M and K.
K lines follow. Each of these lines contains two space-separated integers r and c denoting that the cell in row r and column c contains a plant.
Output
For each test case, print a single line containing one integer — the minimum required length of fences.
Constraints
1≤T≤10
1≤N,M≤109
1≤K≤105
1≤r≤N
1≤c≤M
the cells containing plants are pairwise distinct
https://www.codechef.com/APRIL19B/problems/FENCE
firstly Im sorting the vector of pairs by first then second.(1,2 1,3 2,1 2,2)
then Im sorting vector of pairs by second then first.(2,1 1,2 2,2 1,3)
then Im checking if following pairs are having plants in their adjacent cells or not by checking if adjacent pairs are present in vector of pairs.
its taking O(nlogn) time then also Im getting tle.
Someone please explain me why Im getting tle.
You want to build fences in the field in such a way that the following conditions hold for each cell that contains a plant:
it is possible to move from this cell to each adjacent cell containing a plant without crossing any fences
it is impossible to move from this cell to any cell containing weeds or to leave the grid without crossing any fences
The fences can only be built between cells or on the boundary of the grid, i.e. on the sides of cells. The total length of the built fences is the number of pairs of side-adjacent cells such that there is a fence built on their common side plus the number of sides of cells on the boundary of the grid which have fences built on them. Find the minimum required total length of fences that need to be built.
Input
The first line of the input contains a single integer T denoting the number of test cases. The description of T test cases follows.
The first line of each test case contains three space-separated integers N, M and K.
K lines follow. Each of these lines contains two space-separated integers r and c denoting that the cell in row r and column c contains a plant.
Output
For each test case, print a single line containing one integer — the minimum required length of fences.
Constraints
1≤T≤10
1≤N,M≤109
1≤K≤105
1≤r≤N
1≤c≤M
the cells containing plants are pairwise distinct
https://www.codechef.com/APRIL19B/problems/FENCE
firstly Im sorting the vector of pairs by first then second.(1,2 1,3 2,1 2,2)
then Im sorting vector of pairs by second then first.(2,1 1,2 2,2 1,3)
then Im checking if following pairs are having plants in their adjacent cells or not by checking if adjacent pairs are present in vector of pairs.
its taking O(nlogn) time then also Im getting tle.
Someone please explain me why Im getting tle.
Last edited on Apr 9, 2019 at 9:06pm
Apr 10, 2019 at 1:22am
your search is not clear
you want to check pair (a,b) so do binary search on `a' ¿and then what? you've got a lot of points (a,_) ¿how do you find in constant time (a,b)?
you want to check pair (a,b) so do binary search on `a' ¿and then what? you've got a lot of points (a,_) ¿how do you find in constant time (a,b)?
Apr 10, 2019 at 2:41am
Holy frigg I hate double posts.
http://www.cplusplus.com/forum/general/252101/
http://www.cplusplus.com/forum/general/252101/
Apr 10, 2019 at 2:53am| Holy frigg I hate double posts. |
Especially aggravating for me is the CodeChef challenge cheating.
Apr 10, 2019 at 4:06am
@ne555 for any point (a,b) finding first and last occurance of a in log n time, then finding b in that range in log n (that'd take very less time than log n) .
Apr 10, 2019 at 4:13am
@furry guy, sir I'm not cheating, I just have a doubt that why a k log k solution is giving tle when k <=10^5. I just wanna ask if my logic is correct and I've to optimize the code or I should find some other way to do this.
Apr 10, 2019 at 10:26am
You should know that the CodeChef adjudicators are aware that people have been using this forum to cheat, and have disqualified people for doing so. Proceed at your own risk.
Apr 10, 2019 at 1:20pm
got it. instead of using binary search I used maps and then time limit didn't exceeded.
Apr 10, 2019 at 1:49pm
don't know what was thinking the first time, binary search should have worked.
however, don't understand why you make the second sort.
perhaps you may provide your code so we look at it.
@Duthomhas: ¿what's the idea of your O(n) solution?
however, don't understand why you make the second sort.
perhaps you may provide your code so we look at it.
@Duthomhas: ¿what's the idea of your O(n) solution?
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