LeetCode 980. Unique Paths III

On a 2-dimensional grid, there are 4 types of squares:

1 represents the starting square. There is exactly one starting square.
2 represents the ending square. There is exactly one ending square.
0 represents empty squares we can walk over.
-1 represents obstacles that we cannot walk over.
Return the number of 4-directional walks from the starting square to the ending square, that walk over every non-obstacle square exactly once.

Example 1:

Input: [[1,0,0,0],[0,0,0,0],[0,0,2,-1]]
Output: 2
Explanation: We have the following two paths:
1. (0,0),(0,1),(0,2),(0,3),(1,3),(1,2),(1,1),(1,0),(2,0),(2,1),(2,2)
2. (0,0),(1,0),(2,0),(2,1),(1,1),(0,1),(0,2),(0,3),(1,3),(1,2),(2,2)
Example 2:

Input: [[1,0,0,0],[0,0,0,0],[0,0,0,2]]
Output: 4
Explanation: We have the following four paths:
1. (0,0),(0,1),(0,2),(0,3),(1,3),(1,2),(1,1),(1,0),(2,0),(2,1),(2,2),(2,3)
2. (0,0),(0,1),(1,1),(1,0),(2,0),(2,1),(2,2),(1,2),(0,2),(0,3),(1,3),(2,3)
3. (0,0),(1,0),(2,0),(2,1),(2,2),(1,2),(1,1),(0,1),(0,2),(0,3),(1,3),(2,3)
4. (0,0),(1,0),(2,0),(2,1),(1,1),(0,1),(0,2),(0,3),(1,3),(1,2),(2,2),(2,3)
Example 3:

Input: [[0,1],[2,0]]
Output: 0
Explanation:
There is no path that walks over every empty square exactly once.
Note that the starting and ending square can be anywhere in the grid.

Note:

1 <= grid.length * grid[0].length <= 20

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void uniquePathsIIILogic(int** grid, int gridSize, int gridColSize, int nowRow, int nowCol, int* cnt, int depthLeft){
if(depthLeft<0 || nowRow<0||nowRow>=gridSize||nowCol<0||nowCol>=gridColSize){
return;
}

if(depthLeft==0){
if(grid[nowRow][nowCol]==2){
++*cnt;
}
}
else if(grid[nowRow][nowCol]==2){
return;
}
else if(grid[nowRow][nowCol]>=0){
grid[nowRow][nowCol]-=3;

uniquePathsIIILogic(
grid,gridSize,gridColSize,nowRow-1,nowCol,cnt,depthLeft-1
);
uniquePathsIIILogic(
grid,gridSize,gridColSize,nowRow+1,nowCol,cnt,depthLeft-1
);
uniquePathsIIILogic(
grid,gridSize,gridColSize,nowRow,nowCol-1,cnt,depthLeft-1
);
uniquePathsIIILogic(
grid,gridSize,gridColSize,nowRow,nowCol+1,cnt,depthLeft-1
);

grid[nowRow][nowCol]+=3;

}
}

int uniquePathsIII(int** grid, int gridSize, int* gridColSize){
int startRow, startCol, depth=1;
for(int i=0;i<gridSize;++i){
for(int j=0;j<*gridColSize;++j){
if(grid[i][j]==1){
startRow=i;
startCol=j;
}
else if(grid[i][j]==0){
++depth;
}
}
}
int cnt = 0;
uniquePathsIIILogic(grid,gridSize,*gridColSize,startRow,startCol,&cnt,depth);
return cnt;

}

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