Snakes on a Grid CodeChef Solution
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We Are Discuss About CODECHEF SOLUTION
Snakes on a Grid CodeChef Solution
Problem
There is an �� grid, with rows numbered 1 to � from top to bottom and columns numbered 1 to � from left to right. The cell at the intersection of row � and column � is denoted (�,�).
Chef is standing at cell (1,1) of the grid, and would like to get to cell (�,�). To do this, he can move one step up/down/left/right from the cell he’s standing at, as long as he remains within the grid.
That is, from cell (�,�) he can move to one of {(�−1,�),(�+1,�),(�,�−1),(�,�+1)}.
Unfortunately, there are snakes in the grid!
Each snake has an initial cell (��,��), and a direction ��. The direction is one of 'U'
, 'D'
, 'L'
, or 'R'
– denoting up, down, left, and right respectively. This snake acts as follows:
- In the beginning, it occupies only point (��,��).
- At the end of each second, it will extend one unit in its respective direction.
For example, if (��,��)=(4,7) and ��=L, then:- At first, this snake occupies (4,7)
- After one second, it occupies (4,7) and (4,6) (i.e, it occupies one point more to the left).
- After another second, it occupies (4,7),(4,6), and (4,5); and so on.
Snakes stop extending when they reach the boundary of the grid.
Multiple snakes are allowed to occupy the same cell.
Chef calls a point dangerous if at least one snake occupies it.
The danger of a path from (1,1) to (�,�) is the number of dangerous points it contains.
Help Chef answer � queries of the following form:
- Given �, what’s the minimum danger of a path from (1,1) to (�,�) at the start of time �?
Input Format
- The first line of each test case contains two space-separated integers � and � — the size of the grid and the number of queries.
- The next � lines describe the grid. The �-th of them contains a string �� of length �, denoting row �.
- Each character of the string is one of five from
".LRUD"
, where'.'
denotes an empty cell and the other four denote a snake at that cell with the specified direction. - The next � lines describe the queries. The �-th of them contains a single integer ��, the time for the �-th query.
Output Format
For each test case, output � lines. The �-th of them should contain a single integer: the answer to the �-th query.
Constraints
- 1≤�≤300
- 1≤�≤2⋅105
- 1≤��≤106
- �� contains only the characters
".LRUD
“.
Sample 1:
5 3 ....L ..D.. ..... R..U. ..... 1 3 6
0 1 3
Explanation:
The initial grid looks as follows:
with one possible path from (1,1) to (5,5) marked out, that has danger 0.
This is the answer to the first query.
The second query has �=3, meaning we’re at the start of the third second. All snakes have moved twice (recall that snakes move at the end of a second). One possible path with danger 1 now is:
The third query is �=6, so all snakes have moved five times. One optimal path with danger 3 is:
Note that the cells (1,1) and/or (�,�) may themselves be dangerous, in which case they must be counted into the answer as well.
6 digit code appear after 69 seconds.
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