[LeetCode][JavaScript]Insert Interval

Insert Interval

Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary).

You may assume that the intervals were initially sorted according to their start times.

Example 1:
Given intervals [1,3],[6,9], insert and merge [2,5] in as [1,5],[6,9].

Example 2:
Given [1,2],[3,5],[6,7],[8,10],[12,16], insert and merge [4,9] in as [1,2],[3,10],[12,16].

This is because the new interval [4,9] overlaps with [3,5],[6,7],[8,10].

https://leetcode.com/problems/insert-interval/

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Javascript return的格式是错的，好坑啊。

情况比较多，先全部列出来，大致上是五种，然后找找规律。

1. newInterval可以直接放进去，没有重叠

console.log(JSON.stringify(insert([{start:3,end:4}], {start:5,end:6})) == JSON.stringify([[3,4],[5,6]]));
console.log(JSON.stringify(insert([{start:5,end:6}], {start:3,end:4})) == JSON.stringify([[3,4],[5,6]]));
console.log(JSON.stringify(insert([{start:3,end:4}, {start:8,end:9}], {start:6,end:7})) == JSON.stringify([[3,4],[6,7],[8,9]]));

2.newInterval与一个区间交叉

console.log(JSON.stringify(insert([{start:3,end:8}], {start:1,end:5})) == JSON.stringify([[1,8]]));
console.log(JSON.stringify(insert([{start:3,end:8}], {start:5,end:10})) == JSON.stringify([[3,10]]));

3.newInterval 与左右2个区间交叉

console.log(JSON.stringify(insert([{start:3,end:5}, {start:9,end:11}], {start:4,end:10})) == JSON.stringify([[3,11]]));

4.newInterval “吃掉”了一个或多个区间

console.log(JSON.stringify(insert([{start:3,end:5}, {start:7,end:8}], {start:2,end:9})) == JSON.stringify([[2,9]]));

5.既有交叉，又“吃掉”了区间

console.log(JSON.stringify(insert([{start:3,end:5}, {start:6,end:7},{start:9,end:11}], {start:4,end:10})) == JSON.stringify([[3,11]]));
console.log(JSON.stringify(insert([{start:1,end:3}, {start:5,end:6}], {start:2,end:7})) == JSON.stringify([[1,7]]));

遍历给定数组里的所有区间，总结下来是4种情况，

当前区间记做curr，需要插入的区间记做newInterval

1. curr.end小于newInterval.start，curr可以直接塞进结果；

2. newInterval.end小于curr.start，newInterval和curr都要塞进结果；

3. newInterval的start或者end与curr交叉，merge两个区间，start以小的为准，end以大的为准；

4. newInterval“吃掉了”curr，什么都不做。

解法：

/**
 * Definition for an interval.
 * function Interval(start, end) {
 *     this.start = start;
 *     this.end = end;
 * }
 */
/**
 * @param {Interval[]} intervals
 * @param {Interval} newInterval
 * @return {Interval[]}  !!!!!!! wrong format
 */
var insert = function(intervals, newInterval) {
    var res = [];
    var isInserted = false;
    for(var i = 0; i < intervals.length; i++){
        var curr = intervals[i];
        if(curr.end < newInterval.start || isInserted){
            res.push([curr.start, curr.end]);
        }else if(newInterval.end < curr.start && !isInserted){
            res.push([newInterval.start, newInterval.end]);
            res.push([curr.start, curr.end]);
            isInserted= true;
        }else if(curr.start <= newInterval.start || newInterval.end <= curr.end){ //merge
            newInterval.start = Math.min(curr.start, newInterval.start);
            newInterval.end = Math.max(curr.end, newInterval.end);
        }else{
            // newInterval eat curr
        }
    }

    if(!isInserted){
        res.push([newInterval.start, newInterval.end]);
    }

    return res;
};