**Interval Union - Amazon Top Interview Questions**

### Problem Statement :

Given a two-dimensional integer list intervals representing unsorted inclusive intervals, return their union in sorted order. Constraints n ≤ 100,000 where n is the length of intervals Example 1 Input intervals = [ [0, 5], [4, 6] ] Output [ [0, 6] ] Example 2 Input intervals = [ [1, 2], [3, 4] ] Output [ [1, 2], [3, 4] ] Example 3 Input intervals = [ [5, 6], [1, 2] ] Output [ [1, 2], [5, 6] ]

### Solution :

` ````
Solution in C++ :
vector<vector<int>> solve(vector<vector<int>>& intervals) {
sort(intervals.begin(), intervals.end());
vector<vector<int>> ans;
if (intervals.size() == 0) {
return {};
}
int mini = intervals[0][0], maxi = intervals[0][1];
for (int i = 1; i < intervals.size(); i++) {
if (intervals[i][0] > maxi) {
ans.push_back({mini, maxi});
mini = intervals[i][0];
maxi = intervals[i][1];
} else {
if (intervals[i][1] > maxi) {
maxi = intervals[i][1];
}
}
}
ans.push_back({mini, maxi});
return ans;
}
```

` ````
Solution in Python :
class Solution:
def solve(self, intervals):
events = []
OPEN, CLOSE = 0, 1
for start, end in intervals:
events.append((start, OPEN))
events.append((end, CLOSE))
events.sort()
ans = []
prev = 0
balance = 0
for time, event_type in events:
if balance == 0:
prev = time
if event_type == OPEN:
balance += 1
else:
balance -= 1
if balance == 0:
ans.append((prev, time))
return ans
```

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