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Unique Paths II

2024-07-07 19:34:45   226人阅读

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];
    }


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