Merge pull request #22 from theforestvn88/august

0959

Author: theforestvn88

0901-1000/0959_regions_cut_by_slashes.rb

@@ -0,0 +1,68 @@
+# @param {String[]} grid
+# @return {Integer}
+def regions_by_slashes(grid)
+ size = grid.length
+ # map each slash to three '1' squares, others are '0'
+ # 0 0 1 0 0 
+ # 0 1 0 1 0
+ # 1 0 0 0 1 
+ # 0 1 0 1 0
+ # 0 0 1 0 0
+ # 
+ # oserved that a region is some connected '0' separeting by '1'
+ # so we could count number of regions by counting regions of connected '0'
+ #
+ # Note: why split slash into 3, not 2
+ # consider this: ["//", "//"]
+ # 2 3
+ # 0 1 1 | 0 0 1 0 1
+ # 1 1 1 | 0 1 0 1 0
+ # 1 1 0 | 1 0 1 0 1
+ # | 0 1 0 1 0
+ # | 1 0 1 0 0
+ # as you can see, the right map is correct, there're 4 regions
+ map = Array.new(size * 3) { Array.new(size * 3, 0) }
+
+ i = 0
+ while i < size
+ j = 0
+ while j < size
+ if grid[i][j] == '/'
+ map[i*3][j*3+2] = 1
+ map[i*3+1][j*3+1] = 1
+ map[i*3+2][j*3] = 1
+ elsif grid[i][j] == '\\'
+ map[i*3][j*3] = 1
+ map[i*3+1][j*3+1] = 1
+ map[i*3+2][j*3+2] = 1
+ end
+ j += 1
+ end
+ i += 1
+ end
+
+ # depth-first-search to map all connected '0' squares together and count as a region
+ dfs = lambda { |i, j|
+ return if i < 0 || i >= map.size || j < 0 || j >= map.size
+ return if map[i][j] > 0
+
+ map[i][j] = 1
+
+ dfs.call(i+1, j)
+ dfs.call(i-1, j)
+ dfs.call(i, j+1)
+ dfs.call(i, j-1)
+ }
+
+ count = 0
+ (0...map.size).each { |i|
+ (0...map.size).each { |j|
+ if map[i][j] == 0
+ dfs.call(i, j)
+ count += 1
+ end
+ }
+ }
+
+ count
+end