Give mock interview to the peer - Leetcode 56 - Merge intervals

Leetcode 56_Merge Intervals_Mock Interview.

Given a collection of intervals, merge all overlapping intervals.

For example,
Given [1,3],[2,6],[8,10],[15,18],
return [1,6],[8,10],[15,18].

// Approach:
// - Maintain an interval array, initially an empty array
// - Try to insert an interval1 into the array,
//    We should insert, if and only if there is no overlapping interval in the array with interval1

// input: [1,3],[2,6],[8,10],[15,18]
// 1. ans = []
// -> Try to insert [1, 3]
// -> directly append because of an empty array,
// Now: ans = [[1, 3]]
// 2. ans = [[1, 3]], try to insert [2, 6] -> interval
// Loop through ans, let's say we are iterating i from 0 to ans.length
// ans[i], there is a overlap if, 
//    ans[i][0] <= interval[0] <= ans[i][1] OR
//    ans[i][0] <= interval[1] <= ans[i][1]
// ans[i][0] = Math.min(ans[i][0], interval[0])
// ans[i][1] = Math.max(ans[i][1], interval[1])

// Time Complexity: O(N^2)
// Space Complexity: O(N)