问题
I have a object in 2d array and i want to traverse through them top, left, right for that object acutally i want to check if there are making some loop or better making some closed region. See this picture for better explanation.
Acutally i have a X x Y of slot and when user touch on any of the region it adds the brick there so what i want to do is every time user add a brick check if it is making a close path.
I have writen recursive function for that but it's not working fine it always go for the top only and not right and left. Here is the code
function checkTrap(y,x)
if all_tiles[y][x].state == "changed" then --if brick is added at that location
last_move_y = y
last_move_x = x
--check for top
y = y - 1
if( y >= 1 and y <= 6 and (last_move_y ~= y or last_move_x ~= x) ) then
print("Moved to top at"..y..", "..x)
return checkTrap(y, x)
end
--check for bottom
y = y + 1
if( y >= 1 and y <= 6 and (last_move_y ~= y or last_move_x ~= x) ) then
print("Moved to bottom at"..y..", "..x)
return checkTrap(y, x)
end
--check for left
x = x - 1
if( x >= 1 and x <= 6 and (last_move_y ~= y or last_move_x ~= x) ) then
print("Moved to left at"..y..", "..x)
return checkTrap(y, x)
end
--check for right
x = x + 1
if( x >= 1 and x <= 6 and (last_move_y ~= y or last_move_x ~= x) ) then
print("Moved to right at"..y..", "..x)
return checkTrap(y, x)
end
elseif all_tiles[y][x] == object then
print("it's a loop"..y..", "..x)
return true;
else
print("not changed")
return false
end
end
Edit : New Solution
function findClosedRegion()
local currFlag, isClose = -1, false
local isVisited = {
{-1, -1, -1, -1, -1, -1},
{-1, -1, -1, -1, -1, -1},
{-1, -1, -1, -1, -1, -1},
{-1, -1, -1, -1, -1, -1},
{-1, -1, -1, -1, -1, -1},
{-1, -1, -1, -1, -1, -1}}
local k, m = 1, 1
while k <= 6 and not isClose
do
print("K "..k)
while m <= 6 and not isClose
do
print("M "..m)
if not isBrick[k][m] and isVisited[k][m] == -1 then
local cellsi = Stack:Create()
local cellsj = Stack:Create()
cellsi:push(k)
print("Pushed k "..k)
cellsj:push(m)
print("Pushed m "..m)
currFlag = currFlag + 1
isClose = true
while cellsi:getn() > 0 and isClose do
local p = cellsi:pop()
print("Pop p "..p)
local q = cellsj:pop()
print("Pop q "..q)
if( p >= 1 and p <= 6 and q >= 1 and q <= 6 ) then
if(not isBrick[p][q]) then
print("white ")
if(isVisited[p][q] == -1) then
print("invisited")
isVisited[p][q] = currFlag
cellsi.push(p - 1)
cellsj.push(q)
cellsi.push(p + 1)
cellsj.push(q)
cellsi.push(p)
cellsj.push(q + 1)
cellsi.push(p)
cellsj.push(q - 1)
cellsi:list()
else
if(isVisited[p][q] < currFlag) then
print("visited < currFlag")
isClose = false
end
end
end
else
isClose = false
end --p and q if ends here
end -- tile while end
else
--print("changed and not -1")
end
m = m + 1
end -- m while end
if(isClose) then
print("Closed path")
end
m = 1
k = k + 1
end -- k while end
end
回答1:
The structure of the implementation does not recurse into other directions as only the first branch is called; somehow all neighbors should be included. Apparently you try to implement a kind of Deph-first search on your array. The approach seems absolutely rightm, but all neighbors of a cell have to be taken into account. What perhaps would help most would be to do a connected component analysis and fill all the connected components which touch the border.
回答2:
EDITED:
Instead if searching with the help of black cells, we should search with white cells because your goal is to find area bound by black cells, even if diagonally adjacent. We should find a group of white cells which is only bordered by black cells and not by the border of the whole main grid. That should satisfy your purpose.
JS Fiddle: http://jsfiddle.net/4d4wqer2/
This is the revised algorithm I came up with:
for each cell and until closed area not found
if white and visitedValue = -1
push cell to stack
while stack has values and closed area not found
pop cell from stack
if invalid cell // Cell coordinates are invalid
this area is not closed, so break from the while
else
if white
if visitedValue = -1
{
mark visited
push neighboring four cells to the stack
}
else
if visitedValue > currVisitNumber // The current cells are part of previous searched cell group, which was not a closed group.
this area is not closed, so break from the while
if closed area found
show message
Programmed using JQuery:
function findArea() {
var currFlag = -1, isvisited = [], isClosed = false;
for (var k = 0; k < rows; k++) { // Initialize the isvisited array
isvisited[k] = [];
for (var m = 0; m < cols; m++)
isvisited[k][m] = -1;
}
for (var k = 0; k < rows && !isClosed; k++)
for (var m = 0; m < cols && !isClosed; m++) {
if (!isblack[k][m] && isvisited[k][m] == -1) { // Unvisited white cell
var cellsi = [k], cellsj = [m];
currFlag++;
isClosed = true;
while (cellsi.length > 0 && isClosed) { // Stack has cells and no closed area is found
var p = cellsi.pop(), q = cellsj.pop();
if (p >= 0 && p < rows && q >= 0 && q < cols) { // The cell coord.s are valid
if (!isblack[p][q])
if (isvisited[p][q] == -1) {
isvisited[p][q] = currFlag; // Mark visited
cellsi.push(p - 1); // Push the coord.s of the four adjacent cells
cellsj.push(q);
cellsi.push(p + 1);
cellsj.push(q);
cellsi.push(p);
cellsj.push(q + 1);
cellsi.push(p);
cellsj.push(q - 1);
}
else
if (isvisited[p][q] < currFlag) // The current group of white cells was part of a previous group of white cells which were found to be unbound by the black cells. So, skip this group.
isClosed = false;
}
else
isClosed = false; // The current cell is out of border. Hence skip the whole group.
}
}
}
if (isClosed)
alert('Closed area found');
}
JS Fiddle: http://jsfiddle.net/4d4wqer2/
来源：https://stackoverflow.com/questions/25867647/find-close-path-or-region-using-recursive-method