CODE 70. Unique Paths II

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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.

public int uniquePathsWithObstacles(int[][] obstacleGrid) {
	// Note: The Solution object is instantiated only once and is reused by
	// each test case.
	int m = obstacleGrid.length;
	int n = obstacleGrid[0].length;
	int[][] sum = new int[m][n];
	sum[0][0] = obstacleGrid[0][0] == 1 ? 0 : 1;
	for (int i = 1; i < m; i++) {
		if (obstacleGrid[i][0] == 1) {
			sum[i][0] = 0;
		} else {
			sum[i][0] = sum[i - 1][0];
		}
	}
	for (int i = 1; i < n; i++) {
		if (obstacleGrid[0][i] == 1) {
			sum[0][i] = 0;
		} else {
			sum[0][i] = sum[0][i - 1];
		}
	}
	for (int i = 1; i < m; i++) {
		for (int j = 1; j < n; j++) {
			if (obstacleGrid[i][j] != 1) {
				sum[i][j] = sum[i - 1][j] + sum[i][j - 1];
			} else {
				sum[i][j] = 0;
			}

		}
	}
	return sum[m - 1][n - 1];
}