Check if All the Integers in a Range Are Covered

You are given a 2D integer array ranges and two integers left and right. Each ranges[i] = [starti, endi] represents an inclusive interval between starti and endi.

Return true if each integer in the inclusive range [left, right] is covered by at least one interval in ranges. Return false otherwise.

An integer x is covered by an interval ranges[i] = [starti, endi] if starti <= x <= endi.

Example 1:

Input: ranges = [[1,2],[3,4],[5,6]], left = 2, right = 5
Output: true
Explanation: Every integer between 2 and 5 is covered:
- 2 is covered by the first range.
- 3 and 4 are covered by the second range.
- 5 is covered by the third range.

Example 2:

Input: ranges = [[1,10],[10,20]], left = 21, right = 21
Output: false
Explanation: 21 is not covered by any range.

Approach

C++

#include <bits/stdc++.h>
using namespace std;

bool isCovered(vector<vector<int>> &ranges,
               int left, int right)
{

    set<int> st;

    for (int i = 0; i < ranges.size(); i++)
    {
        for (int j = ranges[i][0]; j <= ranges[i][1]; j++)
        {
            st.insert(j);
        }
    }

    for (int i = left; i <= right; i++)
    {
        if (st.find(i) == st.end())
            return false;
    }
    return true;
}

int main()
{
    vector<vector<int>> ranges = {{1, 2}, {3, 4}, {5, 6}};
    int left = 2, right = 5;

    if (isCovered(ranges, left, right))
        cout << "true\n";
    else
        cout << "false\n";

    return 0;
}