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MergeIntervals.java
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57 lines (55 loc) · 1.73 KB
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/*
Author: King, wangjingui@outlook.com
Date: Dec 20, 2014
Problem: Merge Intervals
Difficulty: Medium
Source: https://oj.leetcode.com/problems/merge-intervals/
Notes:
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: 1. Sort in ascending order of 'start'.
2. Traverse the 'intervals', merge or push...
*/
/**
* Definition for an interval.
* public class Interval {
* int start;
* int end;
* Interval() { start = 0; end = 0; }
* Interval(int s, int e) { start = s; end = e; }
* }
*/
public class Solution {
public List<Interval> merge(List<Interval> intervals) {
Comparator<Interval> comp = new Comparator<Interval>(){
public int compare(Interval a, Interval b) {
if(a.start < b.start) {
return -1;
}else if(a.start > b.start){
return 1;
} else {
if (a.end < b.end) return -1;
else if (a.end > b.end) return 1;
return 0;
}
}
};
ArrayList<Interval> res = new ArrayList<Interval>();
int N = intervals.size();
if (N <= 1) return intervals;
Collections.sort(intervals, comp);
Interval last = intervals.get(0);
for (int i = 0; i < N; ++i) {
if (intervals.get(i).start > last.end) {
res.add(last);
last = intervals.get(i);
} else {
last.end = Math.max(last.end, intervals.get(i).end);
}
}
res.add(last);
return res;
}
}