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16 lines
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16 lines
2.0 KiB
HTML
ZigZagging on a Tree
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<div class="ques-view"><p>Suppose that all the keys in a binary tree are distinct positive integers. A unique binary tree can be determined by a given pair of postorder and inorder traversal sequences. And it is a simple standard routine to print the numbers in level-order. However, if you think the problem is too simple, then you are too naive. This time you are supposed to print the numbers in "zigzagging order" -- that is, starting from the root, print the numbers level-by-level, alternating between left to right and right to left. For example, for the following tree you must output: 1 11 5 8 17 12 20 15.</p>
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<p><img alt="zigzag.jpg" src="https://images.ptausercontent.com/337cbfb0-a7b2-4500-9664-318e9ffc870e.jpg"/></p>
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<h3 id="input-specification-">Input Specification:</h3>
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<p>Each input file contains one test case. For each case, the first line gives a positive integer N (<span class="katex"><span class="katex-mathml"><math><mrow><mo>≤</mo></mrow>\le</math></span><span aria-hidden="true" class="katex-html"><span class="strut" style="height:0.63597em;"></span><span class="strut bottom" style="height:0.7719400000000001em;vertical-align:-0.13597em;"></span><span class="base textstyle uncramped"><span class="mrel">≤</span></span></span></span>30), the total number of nodes in the binary tree. The second line gives the inorder sequence and the third line gives the postorder sequence. All the numbers in a line are separated by a space.</p>
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<h3 id="output-specification-">Output Specification:</h3>
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<p>For each test case, print the zigzagging sequence of the tree in a line. All the numbers in a line must be separated by exactly one space, and there must be no extra space at the end of the line.</p>
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<h3 id="sample-input-">Sample Input:</h3>
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<pre><code class="lang-in">8
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12 11 20 17 1 15 8 5
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12 20 17 11 15 8 5 1
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</code></pre>
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<h3 id="sample-output-">Sample Output:</h3>
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<pre><code class="lang-out">1 11 5 8 17 12 20 15
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</code></pre>
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</div> |