Java: Find possible unique paths considering some obstacles, from top-left corner to bottom-right corner of a specified grid

Last update on May 12 2025 13:12:25 (UTC/GMT +8 hours)

Unique Paths with Obstacles

Write a Java program to find possible unique paths considering some obstacles, from top-left corner to bottom-right corner of a given grid (m x n).

Note: You can move either down or right at any point in time and an obstacle and empty space is marked as 1 and 0 respectively in the grid. Sample grid:
int[][] obstacle_Grid ={
{0, 0, 0},
{0, 1, 0},
{0, 0, 0},
};

Sample Solution:

Java Code:

import java.util.*
public class Solution {
    public static int uniquePaths_With_obstacle_Grid(int[][] obstacle_Grid) {
        // Get the number of rows (m) in the obstacle grid
		int m = obstacle_Grid.length;
		if (m <= 0) {
			return 0;
		}
        // Get the number of columns (n) in the obstacle grid
		int n = obstacle_Grid[0].length;
		if (n <= 0) {
			return 0;
		}
        // Create a dynamic programming array to store unique paths
		int[][] dp = new int[m + 1][n + 1];
		dp[m][n - 1] = 1;

        // Nested loops to iterate through the grid
		for (int i = m - 1; i >= 0; --i) { // Start from the bottom row and move upwards
			for (int j = n - 1; j >= 0; --j) { // Start from the rightmost column and move leftwards
                // Calculate unique paths for the current cell based on obstacles
				dp[i][j] = (obstacle_Grid[i][j] == 0) ? dp[i + 1][j] + dp[i][j + 1] : 0;
			}
		}
        // Return the count of unique paths from top-left to bottom-right corner
		return dp[0][0];
	}
    
  // Main method for testing the uniquePaths_With_obstacle_Grid function
  public static void main(String[] args) {
		int[][] obstacle_Grid ={
            {0, 0, 0}, 
            {0, 1, 0}, 
            {0, 0, 0}, 
        };
		System.out.println("Unique paths from top-left corner to bottom-right corner of the said grid (considering some obstacles): "+uniquePaths_With_obstacle_Grid(obstacle_Grid));
	}		
}

Sample Output:

Unique paths from top-left corner to bottom-right corner of the said grid (considering some obstacles): 2s

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Java program to calculate unique paths in a grid where obstacles appear randomly after every step.
• Write a Java program to find unique paths in a grid where some cells allow only rightward movement and others allow only downward movement.
• Write a Java program to find unique paths in a grid where an obstacle can be removed once per journey.
• Write a Java program to determine the number of paths in a grid where an obstacle teleports you to another random position.

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