unique-paths-ii.md

<p>A robot is located at the top-left corner of a <em>m</em> x <em>n</em> grid (marked &#39;Start&#39; in the diagram below).</p>

<p>The robot can only move either down or right at any point in time. The robot is trying to reach the bottom-right corner of the grid (marked &#39;Finish&#39; in the diagram below).</p>

<p>Now consider if some obstacles are added to the grids. How many unique paths would there be?</p>

<p><img src="https://assets.leetcode.com/uploads/2018/10/22/robot_maze.png" style="width: 400px; height: 183px;" /></p>

<p>An obstacle and empty space is marked as <code>1</code> and <code>0</code> respectively in the grid.</p>

<p><strong>Note:</strong> <em>m</em> and <em>n</em> will be at most 100.</p>

<p><strong>Example 1:</strong></p>

<pre>
<strong>Input:
</strong>[
&nbsp; [0,0,0],
&nbsp; [0,1,0],
&nbsp; [0,0,0]
]
<strong>Output:</strong> 2
<strong>Explanation:</strong>
There is one obstacle in the middle of the 3x3 grid above.
There are two ways to reach the bottom-right corner:
1. Right -&gt; Right -&gt; Down -&gt; Down
2. Down -&gt; Down -&gt; Right -&gt; Right
</pre>