1893. Check if All the Integers in a Range Are Covered

Problem

Tags: Array, Hash Table, Prefix Sum

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.

Constraints:

• 1 <= ranges.length <= 50
• 1 <= starti <= endi <= 50
• 1 <= left <= right <= 50

Code

JS

// 1893. Check if All the Integers in a Range Are Covered (12/10/53416)
// Runtime: 80 ms (49.37%) Memory: 38.79 MB (94.94%) 

/**
 * @param {number[][]} ranges
 * @param {number} left
 * @param {number} right
 * @return {boolean}
 */
var isCovered = function(ranges, left, right) {
    let s = new Set();
    for(let i = left; i <= right; i++) s.add(i);
    
    for(let i = 0; i < ranges.length; i++) {
        for(let j = ranges[i][0]; j <= ranges[i][1]; j++)
            if(s.has(j)) s.delete(j);
    }
    
    return !s.size
};