[LeetCode] 124: Unique Paths II

[Problem]

Follow up for "Unique Paths":

Now consider if some obstacles are added to the grids. How many unique paths would there be?

An obstacle and empty space is marked as 1 and 0 respectively in the grid.

For example,

There is one obstacle in the middle of a 3x3 grid as illustrated below.

[  [0,0,0],  [0,1,0],  [0,0,0]]

The total number of unique paths is 2.

Note: m and n will be at most 100.

[Solution]

class Solution {
public:
int uniquePathsWithObstacles(vector<vector<int> > &obstacleGrid) {
// Note: The Solution object is instantiated only once and is reused by each test case.
if(obstacleGrid.size() == 0 || obstacleGrid[0].size() == 0)return 0;
int m = obstacleGrid.size(), n = obstacleGrid[0].size();

// initial
int dp[m][n];
for(int i = 0; i < n; ++i){
if(i == 0){
    if(obstacleGrid[0][i] == 1)
        dp[0][i] = 0;
    else
    dp[0][i] = 1;
}
else if(obstacleGrid[0][i] == 1){
dp[0][i] = 0;
}
else{
dp[0][i] = dp[0][i-1];
}
}
for(int i = 0; i < m; ++i){
if(i == 0){
    if(obstacleGrid[i][0] == 1)
        dp[i][0] = 0;
    else
    dp[i][0] = 1;
}
else if(obstacleGrid[i][0] == 1){
dp[i][0] = 0;
}
else{
dp[i][0] = dp[i-1][0];
}
}

// dp
for(int i = 1; i < m; ++i){
for(int j = 1; j < n; ++j){
if(obstacleGrid[i][j] == 1){
dp[i][j] = 0;
}
else{
dp[i][j] = dp[i-1][j] + dp[i][j-1];
}
}
}
return dp[m-1][n-1];
}
};

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