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_63.java
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_63.java
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package com.fishercoder.solutions;
public class _63 {
public static class Solution1 {
/**
* Idea: grid[i][j] has to be set to zero if obstacleGrid[i][j] == 1, otherwise, we can get
* dp[i][j] from its top and left dp.
*/
public int uniquePathsWithObstacles(int[][] obstacleGrid) {
if (obstacleGrid == null || obstacleGrid.length == 0) {
return 0;
}
int height = obstacleGrid.length;
int width = obstacleGrid[0].length;
int[][] dp = new int[height][width];
dp[0][0] = obstacleGrid[0][0] == 1 ? 0 : 1;
for (int i = 1; i < height; i++) {
dp[i][0] = obstacleGrid[i][0] == 1 ? 0 : dp[i - 1][0];
}
for (int j = 1; j < width; j++) {
dp[0][j] = obstacleGrid[0][j] == 1 ? 0 : dp[0][j - 1];
}
for (int i = 1; i < height; i++) {
for (int j = 1; j < width; j++) {
if (obstacleGrid[i][j] == 1) {
dp[i][j] = 0;
} else {
int paths = 0;
if (obstacleGrid[i - 1][j] == 0) {
paths += dp[i - 1][j];
}
if (obstacleGrid[i][j - 1] == 0) {
paths += dp[i][j - 1];
}
dp[i][j] = paths;
}
}
}
return dp[height - 1][width - 1];
}
}
}