CODE 70: 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.

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];}