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42 lines
1.7 KiB
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42 lines
1.7 KiB
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<p>给你二叉树的根节点 <code>root</code> 和一个表示目标和的整数 <code>targetSum</code> 。判断该树中是否存在 <strong>根节点到叶子节点</strong> 的路径，这条路径上所有节点值相加等于目标和 <code>targetSum</code> 。如果存在，返回 <code>true</code> ；否则，返回 <code>false</code> 。</p>
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<p><strong>叶子节点</strong> 是指没有子节点的节点。</p>
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<p> </p>
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<p><strong>示例 1：</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2021/01/18/pathsum1.jpg" style="width: 500px; height: 356px;" />
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<pre>
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<strong>输入：</strong>root = [5,4,8,11,null,13,4,7,2,null,null,null,1], targetSum = 22
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<strong>输出：</strong>true
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<strong>解释：</strong>等于目标和的根节点到叶节点路径如上图所示。
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</pre>
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<p><strong>示例 2：</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2021/01/18/pathsum2.jpg" />
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<pre>
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<strong>输入：</strong>root = [1,2,3], targetSum = 5
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<strong>输出：</strong>false
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<strong>解释：</strong>树中存在两条根节点到叶子节点的路径：
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(1 --> 2): 和为 3
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(1 --> 3): 和为 4
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不存在 sum = 5 的根节点到叶子节点的路径。</pre>
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<p><strong>示例 3：</strong></p>
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<pre>
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<strong>输入：</strong>root = [], targetSum = 0
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<strong>输出：</strong>false
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<strong>解释：</strong>由于树是空的，所以不存在根节点到叶子节点的路径。
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</pre>
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<p> </p>
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<p><strong>提示：</strong></p>
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<ul>
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<li>树中节点的数目在范围 <code>[0, 5000]</code> 内</li>
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<li><code>-1000 <= Node.val <= 1000</code></li>
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<li><code>-1000 <= targetSum <= 1000</code></li>
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</ul>
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