56. Merge Intervals

Given a collection of intervals, merge all overlapping intervals.

Example 1:

Input: [[1,3],[2,6],[8,10],[15,18]]
Output: [[1,6],[8,10],[15,18]]
Explanation: Since intervals [1,3] and [2,6] overlaps, merge them into [1,6].

Example 2:

Input: [[1,4],[4,5]]
Output: [[1,5]]
Explanation: Intervals [1,4] and [4,5] are considered overlapping.

这题还是挺简单的，先将intervals按左边界升序，如果左边界相同，就按右边界升序的规则排序，然后依次合并就行了

要注意两点，1) 区间包含的情况

                      2) intervals 的结构为   [{start: xx, end: xx}, {...}] （javaScript是这样的）

/**
 * Definition for an interval.
 * function Interval(start, end) {
 *     this.start = start;
 *     this.end = end;
 * }
 */
/**
 * @param {Interval[]} intervals
 * @return {Interval[]}
 */
var merge = function(intervals) {
    intervals.sort((x, y) => {
        if(x.start - y.start) return x.start - y.start
        return x.end - y.end
    })
    let len = intervals.length
    let ans = []
    let first, end
    if(len) {
        first = intervals[0].start
        end = intervals[0].end
    }else return []
    for(let i = 1;  i < len; i ++) {
        left = intervals[i].start
        right = intervals[i].end
        if(end >= left) {
            if(right > end) end = right 
        }else {
            ans.push({
                start: first,
                end: end
            })
            first = left
            end = right
        }
    }
    ans.push({ 
        start: first,
        end: end
    })
    return ans
};