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36 lines
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36 lines
2.0 KiB
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<p>Given a<strong> directed acyclic graph</strong>, with <code>n</code> vertices numbered from <code>0</code> to <code>n-1</code>, and an array <code>edges</code> where <code>edges[i] = [from<sub>i</sub>, to<sub>i</sub>]</code> represents a directed edge from node <code>from<sub>i</sub></code> to node <code>to<sub>i</sub></code>.</p>
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<p>Find <em>the smallest set of vertices from which all nodes in the graph are reachable</em>. It's guaranteed that a unique solution exists.</p>
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<p>Notice that you can return the vertices in any order.</p>
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<p> </p>
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<p><strong>Example 1:</strong></p>
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<p><img alt="" src="https://assets.leetcode.com/uploads/2020/07/07/untitled22.png" style="width: 231px; height: 181px;" /></p>
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<pre>
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<strong>Input:</strong> n = 6, edges = [[0,1],[0,2],[2,5],[3,4],[4,2]]
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<strong>Output:</strong> [0,3]
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<b>Explanation: </b>It's not possible to reach all the nodes from a single vertex. From 0 we can reach [0,1,2,5]. From 3 we can reach [3,4,2,5]. So we output [0,3].</pre>
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<p><strong>Example 2:</strong></p>
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<p><img alt="" src="https://assets.leetcode.com/uploads/2020/07/07/untitled.png" style="width: 201px; height: 201px;" /></p>
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<pre>
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<strong>Input:</strong> n = 5, edges = [[0,1],[2,1],[3,1],[1,4],[2,4]]
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<strong>Output:</strong> [0,2,3]
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<strong>Explanation: </strong>Notice that vertices 0, 3 and 2 are not reachable from any other node, so we must include them. Also any of these vertices can reach nodes 1 and 4.
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</pre>
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<p> </p>
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<p><strong>Constraints:</strong></p>
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<ul>
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<li><code>2 <= n <= 10^5</code></li>
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<li><code>1 <= edges.length <= min(10^5, n * (n - 1) / 2)</code></li>
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<li><code>edges[i].length == 2</code></li>
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<li><code>0 <= from<sub>i,</sub> to<sub>i</sub> < n</code></li>
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<li>All pairs <code>(from<sub>i</sub>, to<sub>i</sub>)</code> are distinct.</li>
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</ul>
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