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Commit 51a7e97

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author
Shuo
authored
Merge pull request #759 from openset/develop
Add: Minimum Depth of Binary Tree
2 parents 058e139 + ad4abce commit 51a7e97

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‎problems/3sum/README.md‎

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1. [3Sum Closest](../3sum-closest) (Medium)
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1. [4Sum](../4sum) (Medium)
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1. [3Sum Smaller](../3sum-smaller) (Medium)
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### Hints
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<details>
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<summary>Hint 1</summary>
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So, we essentially need to find three numbers x, y, and z such that they add up to the given value. If we fix one of the numbers say x, we are left with the two-sum problem at hand!
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</details>
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<details>
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<summary>Hint 2</summary>
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For the two-sum problem, if we fix one of the numbers, say <pre>x</pre>, we have to scan the entire array to find the next number<pre>y</pre> which is <pre>value - x</pre> where value is the input parameter. Can we change our array somehow so that this search becomes faster?
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</details>
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<details>
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<summary>Hint 3</summary>
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The second train of thought for two-sum is, without changing the array, can we use additional space somehow? Like maybe a hash map to speed up the search?
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</details>

‎problems/bulb-switcher/README.md‎

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</pre>
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### Related Topics
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[[Brainteaser](../../tag/brainteaser/README.md)]
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[[Math](../../tag/math/README.md)]
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[[Brainteaser](../../tag/brainteaser/README.md)]
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### Similar Questions
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1. [Bulb Switcher II](../bulb-switcher-ii) (Medium)

‎problems/container-with-most-water/README.md‎

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### Similar Questions
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1. [Trapping Rain Water](../trapping-rain-water) (Hard)
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### Hints
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<details>
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<summary>Hint 1</summary>
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The aim is to maximize the area formed between the vertical lines. The area of any container is calculated using the shorter line as length and the distance between the lines as the width of the rectangle.
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<pre>
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Area = length of shorter vertical line * distance between lines
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</pre>
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We can definitely get the maximum width container as the outermost lines have the maximum distance between them. However, this container <b>might not be the maximum in size</b> as one of the vertical lines of this container could be really short.
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<br>
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<img src="https://assets.leetcode.com/uploads/2019/10/20/hint_water_trap_1.png" width="500"/>
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<br>
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<img src="https://assets.leetcode.com/uploads/2019/10/20/hint_water_trap_2.png" width="500"/>
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</details>
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<details>
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<summary>Hint 2</summary>
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Start with the maximum width container and go to a shorter width container if there is a vertical line longer than the current containers shorter line. This way we are compromising on the width but we are looking forward to a longer length container.
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</details>

‎problems/count-and-say/README.md‎

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<code>11</code> is read off as <code>&quot;two 1s&quot;</code> or <code>21</code>.<br />
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<code>21</code> is read off as <code>&quot;one 2</code>, then <code>one 1&quot;</code> or <code>1211</code>.</p>
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<p>Given an integer <i>n</i>&nbsp;where 1 &le; <em>n</em> &le; 30, generate the <i>n</i><sup>th</sup> term of the count-and-say sequence.</p>
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<p>Given an integer <i>n</i>&nbsp;where 1 &le; <em>n</em> &le; 30, generate the <i>n</i><sup>th</sup> term of the count-and-say sequence. You can do so recursively, in other words from the previous member&nbsp;read off the digits, counting the number of digits in groups of the same digit.</p>
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<p>Note: Each term of the sequence of integers will be represented as a string.</p>
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<pre>
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<b>Input:</b> 1
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<b>Output:</b> &quot;1&quot;
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<b>Explanation:</b> This is the base case.
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</pre>
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<p><b>Example 2:</b></p>
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<pre>
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<b>Input:</b> 4
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<b>Output:</b> &quot;1211&quot;</pre>
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<b>Output:</b> &quot;1211&quot;
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<b>Explanation:</b> For n = 3 the term was &quot;21&quot; in which we have two groups &quot;2&quot; and &quot;1&quot;, &quot;2&quot; can be read as &quot;12&quot; which means frequency = 1 and value = 2, the same way &quot;1&quot; is read as &quot;11&quot;, so the answer is the concatenation of &quot;12&quot; and &quot;11&quot; which is &quot;1211&quot;.
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</pre>
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### Related Topics
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[[String](../../tag/string/README.md)]

‎problems/count-of-smaller-numbers-after-self/README.md‎

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</pre>
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### Related Topics
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[[Binary Search](../../tag/binary-search/README.md)]
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[[Divide and Conquer](../../tag/divide-and-conquer/README.md)]
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[[Sort](../../tag/sort/README.md)]
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[[Binary Indexed Tree](../../tag/binary-indexed-tree/README.md)]
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[[Segment Tree](../../tag/segment-tree/README.md)]
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[[Binary Search](../../tag/binary-search/README.md)]
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[[Divide and Conquer](../../tag/divide-and-conquer/README.md)]
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### Similar Questions
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1. [Count of Range Sum](../count-of-range-sum) (Hard)

‎problems/create-maximum-number/README.md‎

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</pre>
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### Related Topics
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[[Greedy](../../tag/greedy/README.md)]
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[[Dynamic Programming](../../tag/dynamic-programming/README.md)]
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[[Greedy](../../tag/greedy/README.md)]
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### Similar Questions
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1. [Remove K Digits](../remove-k-digits) (Medium)

‎problems/generalized-abbreviation/README.md‎

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<p>&nbsp;</p>
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### Related Topics
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[[Bit Manipulation](../../tag/bit-manipulation/README.md)]
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[[Backtracking](../../tag/backtracking/README.md)]
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[[Bit Manipulation](../../tag/bit-manipulation/README.md)]
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### Similar Questions
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1. [Subsets](../subsets) (Medium)

‎problems/length-of-last-word/README.md‎

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## [58. Length of Last Word (Easy)](https://leetcode.com/problems/length-of-last-word "最后一个单词的长度")
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<p>Given a string <i>s</i> consists of upper/lower-case alphabets and empty space characters <code>&#39; &#39;</code>, return the length of last word in the string.</p>
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<p>Given a string <i>s</i> consists of upper/lower-case alphabets and empty space characters <code>&#39; &#39;</code>, return the length of last word (last word means the last appearing word if we loop from left to right) in the string.</p>
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<p>If the last word does not exist, return 0.</p>
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<p><b>Note:</b> A word is defined as a character sequence consists of non-space characters only.</p>
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<p><b>Note:</b> A word is defined as a <strong>maximal substring</strong> consisting&nbsp;of non-space characters only.</p>
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<p><b>Example:</b></p>
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‎problems/merge-sorted-array/README.md‎

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### Hints
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<details>
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<summary>Hint 1</summary>
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What if you fill the longer array from the end instead of start ?
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You can easily solve this problem if you simply think about two elements at a time rather than two arrays. We know that each of the individual arrays is sorted. What we don't know is how they will intertwine. Can we take a local decision and arrive at an optimal solution?
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</details>
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<details>
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<summary>Hint 2</summary>
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If you simply consider one element each at a time from the two arrays and make a decision and proceed accordingly, you will arrive at the optimal solution.
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</details>
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package problem111
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import "github.com/openset/leetcode/internal/kit"
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// TreeNode - Definition for a binary tree node.
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type TreeNode = kit.TreeNode
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/**
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* Definition for a binary tree node.
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* type TreeNode struct {
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* Val int
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* Left *TreeNode
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* Right *TreeNode
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* }
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*/
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func minDepth(root *TreeNode) int {
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if root == nil {
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return 0
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}
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l := minDepth(root.Left)
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r := minDepth(root.Right)
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if l == 0 || r == 0 {
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return l + r + 1
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}
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if l < r {
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return l + 1
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}
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return r + 1
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}

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