92 lines
1.8 KiB
Markdown
92 lines
1.8 KiB
Markdown
# Leetcode Merge-Intervals
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#### 2022-09-01 14:04
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> ##### Algorithms:
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>
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> #algorithm #sort
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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_medium
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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/merge-intervals/)
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- [Solution ans Explanation](https://leetcode.com/problems/merge-intervals/solution/)
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---
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### Problem
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Given an array of `intervals` where `intervals[i] = [starti, endi]`, merge all overlapping intervals, and return _an array of the non-overlapping intervals that cover all the intervals in the input_.
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#### Examples
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**Example 1:**
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**Input:** intervals = [[1,3],[2,6],[8,10],[15,18]]
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**Output:** [[1,6],[8,10],[15,18]]
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**Explanation:** Since intervals [1,3] and [2,6] overlap, merge them into [1,6].
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**Example 2:**
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**Input:** intervals = [[1,4],[4,5]]
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**Output:** [[1,5]]
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**Explanation:** Intervals [1,4] and [4,5] are considered overlapping.
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#### Constraints
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- `1 <= intervals.length <= 104`
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- `intervals[i].length == 2`
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- `0 <= starti <= endi <= 104`
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### Thoughts
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> [!summary]
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> This is a generic array problem.
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#### Situations to consider:
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- The intervals can be unordered
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- The first interval
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- `[0, 3] [0, 1]` are adjacent and overlapped.
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To solve the situations, sort first, and use `max` function to solve the 3rd solution.
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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<vector<int>> merge(vector<vector<int>> &intervals) {
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// sort first, so that data are continious
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vector<vector<int>> ans;
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sort(intervals.begin(), intervals.end());
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for (auto interval : intervals) {
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if (ans.empty() || ans.back()[1] < interval[0]) {
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ans.push_back(interval);
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} else {
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ans.back()[1] = max(interval[1], ans.back()[1]);
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}
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}
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return ans;
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}
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};
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```
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