[JS] Interval List Intersections

🔒 문제 (LeetCode 986)

You are given two lists of closed intervals, firstList and secondList, where firstList[i] = [starti, endi] and secondList[j] = [startj, endj]. Each list of intervals is pairwise disjoint and in sorted order.

Return the intersection of these two interval lists.

A closed interval [a, b] (with a <= b) denotes the set of real numbers x with a <= x <= b.

The intersection of two closed intervals is a set of real numbers that are either empty or represented as a closed interval. For example, the intersection of [1, 3] and [2, 4] is [2, 3].

Constraints:

• 0 <= firstList.length, secondList.length <= 1000
• firstList.length + secondList.length >= 1
• 0 <= starti < endi <= 109
• endi < starti+1
• 0 <= startj < endj <= 109
• endj < startj+1

 

🌊 입출력

Example 1:

Input: firstList = [[0,2],[5,10],[13,23],[24,25]], secondList = [[1,5],[8,12],[15,24],[25,26]]
Output: [[1,2],[5,5],[8,10],[15,23],[24,24],[25,25]]

Example 2:

Input: firstList = [[1,3],[5,9]], secondList = []
Output: []

 

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🔑 해결

🌌 알고리즘 - 투포인터

/**
 * @param {number[][]} firstList
 * @param {number[][]} secondList
 * @return {number[][]}
 */
var intervalIntersection = function(firstList, secondList) {
    const result = [];
    let [firstP, secondP] = [0 ,0];
    
    while(firstP < firstList.length && secondP < secondList.length) {
        const maxStart = Math.max(firstList[firstP][0], secondList[secondP][0]);
        const minEnd = Math.min(firstList[firstP][1], secondList[secondP][1]);
        
        if(maxStart <= minEnd) result.push([maxStart, minEnd]);
        
        if(firstList[firstP][1] < secondList[secondP][1]) firstP++;
        else secondP++;
    }
    
    return result;
};