leetcode题目56. 合并区间

题目描述

链接：https://leetcode-cn.com/problems/merge-intervals/
以数组 intervals 表示若干个区间的集合，其中单个区间为 intervals[i] = [starti, endi] 。请你合并所有重叠的区间，并返回 一个不重叠的区间数组，该数组需恰好覆盖输入中的所有区间 。

示例

输入：intervals = [[1,3],[2,6],[8,10],[15,18]]
输出：[[1,6],[8,10],[15,18]]
解释：区间 [1,3] 和 [2,6] 重叠, 将它们合并为 [1,6].

代码

// 题解：https://leetcode-cn.com/problems/merge-intervals/solution/he-bing-qu-jian-by-leetcode-solution/
    public int[][] merge(int[][] intervals) {
        if (intervals == null || intervals.length <= 1) {
            return intervals;
        }
      // 先排序
        Arrays.sort(intervals, new Comparator<int[]>() {
            @Override
            public int compare(int[] t0, int[] t1) {
                return t0[0] - t1[0];
            }
        });

        List<int[]> merged = new ArrayList<>();
        int[] currentElements = new int[]{intervals[0][0], intervals[0][1]};
        merged.add(currentElements);
        for (int i = 1; i < intervals.length; i++) {
            if (intervals[i][0] <= currentElements[1]) {
                currentElements[1] = Math.max(currentElements[1], intervals[i][1]);
            } else {
                int[] temp = new int[]{intervals[i][0], intervals[i][1]};
                merged.add(temp);
                currentElements = temp;
            }
        }
        return merged.toArray(new int[merged.size()][]);
    }