56. Merge Intervals - LeetCode

Question

56. Merge Intervals

Solution

题目大意:

一个坐标轴,给你n个范围,把重叠的范围合并,返回合并后的坐标对

思路:

先排序,再遍历判断下一个开始是否在上一个范围内,如果在且结束坐标大于上一个坐标就合并

Java实现:

public List<Interval> merge(List<Interval> intervals) {
    if (intervals == null || intervals.size() == 0) return intervals;

    // sort
    intervals = intervals.stream()
        .sorted(Comparator.comparing(e -> e.start))
        .collect(Collectors.toList());

    List<Interval> result = new ArrayList<>();
    int start = intervals.get(0).start;
    int end = intervals.get(0).end;
    for (int i = 1; i < intervals.size(); i++) {
        Interval tmp = intervals.get(i);
        if (tmp.start >= start && tmp.start <= end) {
            if (tmp.end > end) end = tmp.end;
        } else {
            result.add(new Interval(start, end));
            start = tmp.start;
            end = tmp.end;
        }
    }
    result.add(new Interval(start, end));
    return result;
}