LeetCode 63 - Unique Paths II

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 1:

public int uniquePathsWithObstacles(int[][] g) {
    if(g[0][0] == 1) return 0;
    int m = g.length;
    int n = g[0].length;
    int[][] f = new int[m][n];
    f[0][0] = 1;
    for(int i=0; i<m; i++) {
        for(int j=0; j<n; j++) {
            if(g[i][j] == 1) {
                f[i][j] = 0;
            } else if(i>0 || j>0){
                f[i][j] = (i>0?f[i-1][j]:0) + (j>0?f[i][j-1]:0);
            }
        }
    }
    return f[m-1][n-1];
}

 

Solution 2:

public int uniquePathsWithObstacles(int[][] g) {
    if(g[0][0] == 1) return 0;
    int m = g.length;
    int n = g[0].length;
    int[] f = new int[n];
    f[0] = 1;
    for(int i=0; i<m; i++) {
        for(int j=0; j<n; j++) {
            if(g[i][j] == 1) {
                f[j] = 0;
            } else if(j>0){
                f[j] = f[j] + f[j-1];
            }
        }
    }
    return f[n-1];
}