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MergeIntervals.java
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MergeIntervals.java
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import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
/**
* Merge Intervals <a href="https://leetcode-cn.com/problems/merge-intervals/">Description</a>
* @author LBW
*/
public class MergeIntervals {
public int[][] merge(int[][] intervals) {
if (intervals == null || intervals.length <= 1)
return intervals;
//sort by the first element.
Arrays.sort(intervals, new Comparator<int[]>() {
@Override
public int compare(int[] o1, int[] o2) {
return o1[0] - o2[0];
}
});
int num = intervals.length;
ArrayList<int[]> results = new ArrayList<>();
int start = intervals[0][0], end = intervals[0][1];
for (int i = 1; i < num; i++) {
if (intervals[i][0] > end) {
results.add(new int[]{start, end});
start = intervals[i][0];
end = Integer.max(intervals[i][1], end);
}
else { // merge
end = intervals[i][1];
}
}
// add the last element.
results.add(new int[]{start ,end});
// store the ArrayList into the array.
return results.toArray(intervals);
}
public static void main(String[] args) {
int[][] test = new int[][]{{2, 6}, {1, 3}, {8, 10}, {15, 18}};
MergeIntervals mergeIntervals = new MergeIntervals();
mergeIntervals.merge(test);
}
}