[leetcode] Unique Path II

要注意corner case的检查

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public class Solution { public int uniquePathsWithObstacles(int[][] obstacleGrid) { if (obstacleGrid == null || obstacleGrid.length == 0 || obstacleGrid[0].length == 0){ return 0; } int row = obstacleGrid.length; int column = obstacleGrid[0].length; int lookup[] = new int[column]; lookup[column-1] = obstacleGrid[row-1][column-1]==1?0:1; for (int i = column-2; i >= 0; i--){ lookup[i] = obstacleGrid[row-1][i] == 1?0:lookup[i+1]; } for (int i = row-2; i >= 0; i--){ lookup[column-1] = obstacleGrid[i][column-1] == 1?0:lookup[column-1]; for (int j = column-2; j >= 0; j--){ lookup[j] = obstacleGrid[i][j] == 1?0:(lookup[j]+lookup[j+1]); } } return lookup[0]; } }