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所以我试图用递归和回溯来解决4x4数独。 当我打电话SolveSmallSudoku(L); “现在解决...” 它给了我这个“错误,(在SolveSmallSudoku中)矩阵索引超出范围” 但我无法发现任何与我的矩阵L有关的索引。这似乎是我的程序没有正确执行我的回溯部分。我认为我的findPossibleEntries过程正常工作。它确实找到了该特定单元格的所有可能值。任何人有任何提示?解决枫4X4数独
> L := Matrix(4,4,[ [0,4,0,0],[2,0,0,3],[4,0,0,1],[0,0,3,0] ]);
> isFull := proc(L)
local x, y;
for x from 1 to 4 do
for y from 1 to 4 do
if L[x,y]=0 then
return false;
end if;
end do;
end do;
return true;
end proc;
>findPossibleEntries := proc(L, i, j)
local x, y, possible:=[0,0,0,0];
local r:=1, c:=1;
#Checking possible entries in ith row
for y from 1 to 4 do
if not L[i,y] = 0 then
possible[L[i,y]] := 1;
end if;
end do;
#Checking possible entries in jth col
for x from 1 to 4 do
if not L[x,j] = 0 then
possible[L[x,j]] := 1;
end if;
end do;
#Checking possible entries block by block
if i >= 1 and i <= 2 then
r := 1;
elif i >= 3 and i <= 4 then
r := 3;
end if;
if j >= 1 and j <= 2 then
c := 1;
elif j >= 3 and j <= 4 then
c := 3;
end if;
#Using for-loop to find possible entries in the block
for x in range(r, r+1) do
for y in range(c, c+1) do
if not L[x,y] = 0 then
possible[L[x,y]] := 1;
end if;
end do;
end do;
#Now the list, possible, only holds the possible entries
for x from 1 to 4 do
if possible[x] = 0 then
possible[x] := x;
else
possible[x] := 0;
end if;
end do;
return possible;
end proc;
>SolveSmallSudoku := proc(L)
local x, y, i:=0, j:=0, possibleVal:=[0,0,0,0];
if isFull(L) then
print("Solved!");
print(L);
return;
else
print("Solving now...");
for x from 1 to 4 do
for y from 1 to 4 do
if L[x,y] = 0 then
i:=x;
j:=y;
break;
end if
end do;
#Breaks the outer loop as well
if L[x,y] = 0 then
break;
end if
end do;
#Finds all the possibilities for i,j
possibleVal := findPossibleEntries(L,i,j);
#Traverses the list, possibleVal to find the correct entries and finishes the sudoku recursively
for x from 1 to 4 do
if not possibleVal[x] = 0 then
L[i,j]:= possibleVal[x];
SolveSmallSudoku(L);
end if;
end do;
#Backtracking
L[i,j]:= 0;
end if;
end proc;
请问您指出y在哪里设置为5? – harre
你可以通过在调试器中运行,或者在外部之前运行'print(x,y)',如果L [x,y] = 0,然后我建议你移除'',你就可以自己看到它。请注意以下常见行为,当结束此循环时,会得到5作为'y'的最终值:'对于y,从1到4做;结束了:y;'。 – acer
感谢您的澄清。你知道这个“通常行为”背后的想法,for循环中的条件是“y <= 4”而不是“y <4”吗? (请注意,我不是OP,为什么我没有对发布的代码进行任何严格的调试。) – harre