[LeetCode 063] Unique Paths II

Unique Paths II

• 左上角那个点：有obstacle，则为0；没有obstacle，则为1。
• 最上一排：有obstacle，则为0；没有obstacle，则为左边元素的值。
• 最左边一排：有obstacle，则为0；没有obstacle，则为上边元素的值。
• 其它点：有obstacle，则为0；没有obstacle，则为上边元素和左边元素值得和。

Implementation

public class Solution {
    public int uniquePathsWithObstacles(int[][] obstacleGrid) {
        int right = obstacleGrid[0].length;
        int down = obstacleGrid.length;
        int[] record = new int[right];
        for (int i = 0; i < down; i++) {
            for (int j = 0; j < right; j++) {
                if (i == 0 && j == 0) {
                    record[j] = (obstacleGrid[i][j] == 1)? 0: 1;
                }
                else if (i == 0) {
                    record[j] = (obstacleGrid[i][j] == 1)? 0: record[j - 1];
                }
                else if (j == 0) {
                    record[j] = (obstacleGrid[i][j] == 1)? 0: record[j];
                }
                else {
                    record[j] = (obstacleGrid[i][j] == 1)? 0: record[j] + record[j - 1];
                }
            }
        }
        return record[right - 1];
    }
}