leetcode -- Merge Intervals

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].

[解题思路]

这里使用Insert interval的解题过程，将待合并的interval依次插入

/**
 * 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 ArrayList<Interval> merge(ArrayList<Interval> intervals) {
        // Start typing your Java solution below
        // DO NOT write main() function
        ArrayList<Interval> result = new ArrayList<Interval>();
        for(int i = 0; i < intervals.size(); i++){
            result = insert(result, intervals.get(i));
        }
        return result;
    }
    
    public ArrayList<Interval> insert(ArrayList<Interval> intervals,
            Interval newInterval) {
        ArrayList<Interval> result = new ArrayList<Interval>();
        for (int i = 0; i < intervals.size(); i++) {
            Interval tmp = intervals.get(i);
            if (newInterval.end < tmp.start) {
                result.add(newInterval);
                for(int j = i; j < intervals.size(); j++){
                    result.add(intervals.get(j));
                }
                return result;
            } else if (newInterval.start > tmp.end) {
                result.add(tmp);
                continue;
            } else {
                newInterval.start = Math.min(tmp.start, newInterval.start);
                newInterval.end = Math.max(tmp.end, newInterval.end);
            }
        }
        result.add(newInterval);
        return result;
    }
}