96 lines
1.4 KiB
Markdown
96 lines
1.4 KiB
Markdown
# Leetcode Pascal's-Triangle-II
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2022-09-02 14:54
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> ##### Algorithms:
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>
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> #algorithm #recursion
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>
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> ##### Data structures:
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>
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> #DS #array
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>
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> ##### Difficulty:
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>
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> #coding_problem #difficulty-easy
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>
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> ##### Additional tags:
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>
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> #leetcode
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>
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> ##### Revisions:
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>
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> N/A
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##### Links:
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- [Link to problem](https://leetcode.com/problems/pascals-triangle-ii/)
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---
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### Problem
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Given an integer `rowIndex`, return the `rowIndexth` (**0-indexed**) row of the **Pascal's triangle**.
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In **Pascal's triangle**, each number is the sum of the two numbers directly above it as shown:
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#### Examples
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**Example 1:**
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**Input:** rowIndex = 3
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**Output:** [1,3,3,1]
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**Example 2:**
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**Input:** rowIndex = 0
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**Output:** [1]
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**Example 3:**
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**Input:** rowIndex = 1
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**Output:** [1,1]
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#### Constraints
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- `0 <= rowIndex <= 33`
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### Thoughts
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> [!summary]
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> This is a #recursion problem.
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Because to get the nth row, we have to get the `n - 1` th
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row, we use recursion.
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### Solution
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```cpp
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class Solution {
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public:
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vector<int> getRow(int rowIndex) {
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// recursion
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if (rowIndex == 0) {
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return {1};
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}
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auto last = getRow(rowIndex - 1);
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vector<int> ans;
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ans.push_back(1);
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for (int i = 1; i < rowIndex; i++) {
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ans.push_back(last[i] + last[i - 1]);
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}
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ans.push_back(1);
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return ans;
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}
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};
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```
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