[LeetCode] 052: Merge Intervals

[Problem]
Given a collection of intervals, merge all overlapping intervals.

For example,

Given

[1,3],[2,6],[8,10],[15,18]

,

return

[1,6],[8,10],[15,18]

.

[Solution]

/**
* Definition for an interval.
* struct Interval {
*     int start;
*     int end;
*     Interval() : start(0), end(0) {}
*     Interval(int s, int e) : start(s), end(e) {}
* };
*/

/**
* Definition for cmp
*/
bool cmp(const Interval &a, const Interval &b){
return a.start < b.start;
}

/**
* Definition for Solution
*/
class Solution {
public:
// merge interval into intervals
void merge(vector<Interval> &intervals, Interval interval){
// intervals is empty
if(intervals.size() == 0){
intervals.push_back(interval);
}
else{
int i = intervals.size()-1;

// not interacted with the last interval
if(interval.start > intervals[i].end){
intervals.push_back(interval);
}
// interacted with the last interval, update the end of the last interval
else{
intervals[i].end = max(intervals[i].end, interval.end);
}
}
}
// merge intervals
vector<Interval> merge(vector<Interval> &intervals) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
vector<Interval> res;

// sort by start
sort(intervals.begin(), intervals.end(), cmp);

// merge
for(int i = 0; i < intervals.size(); ++i){
merge(res, intervals[i]);
}
return res;
}
};

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