Unique Paths II

题目

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.

方法

和上一题一样，只是增加了一些判断条件。

public int uniquePathsWithObstacles(int[][] obstacleGrid) {
if (obstacleGrid == null) {
return 0;
}
int lenX = obstacleGrid.length;
if (lenX == 0) {
return 0;
}
int lenY = obstacleGrid[0].length;
int[][] num = new int[lenX][lenY];
for (int i = 0; i < lenX; i++) {
for (int j = 0; j < lenY; j++) {
if (obstacleGrid[i][j] == 1) {
obstacleGrid[i][j] = 0;
} else {
if (i == 0 && j == 0) {
num[i][j] = 1;
} else if (i == 0) {
num[i][j] = num[i][j - 1];
} else if (j == 0) {
num[i][j] = num[i - 1][j];
} else  {
num[i][j] = num[i - 1][j] + num[i][j - 1];
}
}
}
}
return num[lenX - 1][lenY - 1];
}