[Leetcode] Unique Path II

Problem

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.

Analysis

• Similar to Unique Path except that we need to decide whether a position has obstacle or not
• If yes, the number of ways to it is 0

Code

	public class Solution {
	public int uniquePathsWithObstacles(int[][] grid) {
	int m = grid.length;
	int n = grid[0].length;
	int[] count = new int[n];
	for(int i=0; i<m; i++){
	for(int j=0; j<n; j++){
	//Case 1: has obstacle, then set as zero
	if(grid[i][j]==1) count[j] = 0;
	//Deal with i==0, j==0
	else if(i==0 && j==0) count[j] = 1;
	else if(j==0) count[j] = count[j];
	else count[j] = count[j] + count[j-1];
	}
	}
	return count[n-1];
	}
	}

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