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 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 public static int UniquePathsIIDP(List<List<int>> obstacleGrid) { int m = obstacleGrid.Count; int n = obstacleGrid[0].Count; int[,] grid = new int[m, n]; // if the start point is a obstacle, return 0 if (obstacleGrid[0][0] == 1) return 0; grid[0, 0] = 1; for (int i = 1; i < m; i++) { if (obstacleGrid[i][0] == 0 && grid[i - 1, 0] != 0) grid[i, 0] = 1; else grid[i, 0] = 0; } for (int i = 1; i < n; i++) { if (obstacleGrid[0][i] == 0 && grid[0, i - 1] != 0) grid[0, i] = 1; else grid[0, i] = 0; } for (int i = 1; i < m; i++) { for (int j = 1; j < n; j++) { if (obstacleGrid[i][j] == 1) grid[i, j] = 0; else grid[i, j] = grid[i - 1, j] + grid[i, j - 1]; } } return grid[m - 1, n - 1]; } |
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