986. Interval List Intersections

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986. Interval List Intersections

Description

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].

Example 1:

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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:

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

Constraints:

  • 0 <= firstList.length, secondList.length <= 1000
  • firstList.length + secondList.length >= 1
  • 0 <= starti < endi <= 10^9
  • endi < starti+1
  • 0 <= startj < endj <= 10^9
  • endj < startj+1

Hints/Notes

Solution

Language: C++

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class Solution {
public:
    vector<vector<int>> intervalIntersection(vector<vector<int>>& firstList, vector<vector<int>>& secondList) {
        int i = 0, j = 0, m = firstList.size(), n = secondList.size();
        vector<vector<int>> res;
        while (i < m && j < n) {
            if (firstList[i][1] < secondList[j][0]) {
                i++;
                continue;
            }
            if (secondList[j][1] < firstList[i][0]) {
                j++;
                continue;
            }
            int start = max(firstList[i][0], secondList[j][0]);
            int end = min(firstList[i][1], secondList[j][1]);
            res.push_back({start, end});
            if (firstList[i][1] < secondList[j][1]) {
                i++;
            } else {
                j++;
            }
        }
        return res;
    }
};