leetcode — unique-paths-ii

/**
* Source : https://oj.leetcode.com/problems/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 class UniquePath2 {

/**
* 依然使用动态规划
* 注意障碍，障碍在边上和中间
*
* @param maze
* @return
*/
public int finAllUniquePaths (int[][] maze) {
if (maze.length <= 0 || maze[0].length <= 0) {
return 0;
}
int max = 0;
for (int i = 0; i < maze.length; i++) {
for (int j = 0; j < maze[0].length; j++) {
if (maze[i][j] == 1) {
// 障碍处为0
max = maze[i][j] = 0;
} else {
if (i > 0 && j > 0) {
max = maze[i][j] = maze[i-1][j] + maze[i][j-1];
} else if (i > 0) {
// 第一列不一定是1
max = maze[i][j] = maze[i-1][j];
} else if (j > 0) {
// 第一行不一定是1
max = maze[i][j] = maze[i][j-1];
} else {
// 第一个是1
max = maze[i][j] = 1;
}
}
}
}
return max;
}

public static void main(String[] args) {
UniquePath2 uniquePaths = new UniquePath2();
int[][] arr = new int[][]{
{0,1},
{0,0}
};
int[][] arr1 = new int[][]{
{0,1,0},
{0,0,0}
};
int[][] arr2 = new int[][]{
{0,1,0},
{0,1,0},
{0,0,0}
};
int[][] arr3 = new int[][]{
{0,0,0},
{0,1,0},
{0,0,0}
};
int[][] arr4 = new int[][]{
{0,0,0,0,0,0,0},
{0,1,0,0,0,0,0},
{0,0,0,0,0,0,0}
};
System.out.println(uniquePaths.finAllUniquePaths(arr));
System.out.println(uniquePaths.finAllUniquePaths(arr1));
System.out.println(uniquePaths.finAllUniquePaths(arr2));
System.out.println(uniquePaths.finAllUniquePaths(arr3));
System.out.println(uniquePaths.finAllUniquePaths(arr4));
}

}