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39 lines
1.7 KiB
HTML
<p>You are given a network of <code>n</code> nodes, labeled from <code>1</code> to <code>n</code>. You are also given <code>times</code>, a list of travel times as directed edges <code>times[i] = (u<sub>i</sub>, v<sub>i</sub>, w<sub>i</sub>)</code>, where <code>u<sub>i</sub></code> is the source node, <code>v<sub>i</sub></code> is the target node, and <code>w<sub>i</sub></code> is the time it takes for a signal to travel from source to target.</p>
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<p>We will send a signal from a given node <code>k</code>. Return the time it takes for all the <code>n</code> nodes to receive the signal. If it is impossible for all the <code>n</code> nodes to receive the signal, return <code>-1</code>.</p>
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<p> </p>
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<p><strong>Example 1:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2019/05/23/931_example_1.png" style="width: 217px; height: 239px;" />
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<pre>
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<strong>Input:</strong> times = [[2,1,1],[2,3,1],[3,4,1]], n = 4, k = 2
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<strong>Output:</strong> 2
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</pre>
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<p><strong>Example 2:</strong></p>
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<pre>
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<strong>Input:</strong> times = [[1,2,1]], n = 2, k = 1
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<strong>Output:</strong> 1
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</pre>
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<p><strong>Example 3:</strong></p>
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<pre>
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<strong>Input:</strong> times = [[1,2,1]], n = 2, k = 2
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<strong>Output:</strong> -1
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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>1 <= k <= n <= 100</code></li>
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<li><code>1 <= times.length <= 6000</code></li>
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<li><code>times[i].length == 3</code></li>
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<li><code>1 <= u<sub>i</sub>, v<sub>i</sub> <= n</code></li>
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<li><code>u<sub>i</sub> != v<sub>i</sub></code></li>
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<li><code>0 <= w<sub>i</sub> <= 100</code></li>
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<li>All the pairs <code>(u<sub>i</sub>, v<sub>i</sub>)</code> are <strong>unique</strong>. (i.e., no multiple edges.)</li>
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</ul>
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