**Movie Theatres - Amazon Top Interview Questions**

### Problem Statement :

Given a list of time exclusive intervals for different movie showings (possibly overlapping), find the minimum number of theatres required to be able to show all movies. Constraints 0 ≤ n ≤ 100,000 where n is the length of `intervals Example 1 Input intervals = [ [30, 75], [0, 50], [60, 150] ] Output 2 Explanation [30, 75] and [0, 50] overlap. [30, 75] and [60, 150] also overlap but later on. So the max number here is 2. Example 2 Input intervals = [ [10, 20], [20, 30] ] Output 1 Explanation Boundaries are exclusive so these intervals are not considered overlapping. Example 3 Input intervals = [ [0, 1], [0, 1], [0, 1] ] Output 3 Explanation The three intervals happen all at the same time so we need 3.

### Solution :

` ````
Solution in C++ :
int solve(vector<vector<int>> &intervals) {
map<int, int> m;
for (auto &i : intervals) {
m[i[0]] += 1;
m[i[1]] -= 1;
}
int ans = 0, prev = 0;
for (auto &[x, y] : m) {
ans = max(ans, prev += y);
}
return ans;
}
```

` ````
Solution in Python :
class Solution:
def solve(self, intervals):
events = []
OPEN, CLOSE = 1, 0
# bit of a hack to keep proper sort order, for example [[10, 20], [20, 30]]. We want to prioritize open over close as the answer should be 1
for i, (start, end) in enumerate(intervals):
events.append((start, OPEN, i))
events.append((end, CLOSE, i))
events.sort()
window = set()
ans = 0
for event_time, event_type, idx in events:
if event_type == OPEN:
window.add(idx)
else:
window.remove(idx)
ans = max(ans, len(window))
return ans
```

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