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Formatted question description: https://leetcode.ca/all/1893.html

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

Level

Easy

Description

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

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] = [start_i, end_i] if start_i <= x <= end_i.

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 <= start_i <= end_i <= 50
• 1 <= left <= right <= 50

Solution

Since the data range is limited, for each range in ranges, consider the intersection of range and [left, right], and add all the numbers in the intersection into a hash set. Finally, check whether the hash set’s size is right - left + 1.

• Java
• C++
• Python
• Go
• TypeScript
• Javascript

• class Solution {
      public boolean isCovered(int[][] ranges, int left, int right) {
          Set<Integer> set = new HashSet<Integer>();
          for (int[] range : ranges) {
              int start = Math.max(range[0], left);
              int end = Math.min(range[1], right);
              for (int i = start; i <= end; i++)
                  set.add(i);
          }
          return set.size() == right - left + 1;
      }
  }
  
  ############
  
  class Solution {
      public boolean isCovered(int[][] ranges, int left, int right) {
          int[] diff = new int[52];
          for (int[] range : ranges) {
              int l = range[0], r = range[1];
              ++diff[l];
              --diff[r + 1];
          }
          int cur = 0;
          for (int i = 0; i < diff.length; ++i) {
              cur += diff[i];
              if (i >= left && i <= right && cur == 0) {
                  return false;
              }
          }
          return true;
      }
  }
  

• // OJ: https://leetcode.com/problems/check-if-all-the-integers-in-a-range-are-covered/
  // Time: O(N)
  // Space: O(N)
  class Solution {
  public:
      bool isCovered(vector<vector<int>>& A, int left, int right) {
          unordered_set<int> s;
          for (auto &v : A) {
              for (int i = max(left,v[0]); i <= min(right,v[1]); ++i) {
                  s.insert(i);
              }
          }
          return s.size() == right - left + 1;
      }
  };
  

• class Solution:
      def isCovered(self, ranges: List[List[int]], left: int, right: int) -> bool:
          diff = [0] * 52
          for l, r in ranges:
              diff[l] += 1
              diff[r + 1] -= 1
          cur = 0
          for i, df in enumerate(diff):
              cur += df
              if left <= i <= right and cur == 0:
                  return False
          return True
  
  ############
  
  # 1893. Check if All the Integers in a Range Are Covered
  # https://leetcode.com/problems/check-if-all-the-integers-in-a-range-are-covered/
  
  class Solution:
      def isCovered(self, ranges: List[List[int]], left: int, right: int) -> bool:
          A = [0] * 52
          
          for start,end in ranges:
              A[start] += 1
              A[end + 1] -= 1
          
          for i in range(1, 52):
              A[i] += A[i - 1]
  
          for i in range(left, right + 1):
              if A[i] <= 0: return False
          
          return True
  
  

• func isCovered(ranges [][]int, left int, right int) bool {
  	diff := [52]int{}
  	for _, rg := range ranges {
  		l, r := rg[0], rg[1]
  		diff[l]++
  		diff[r+1]--
  	}
  	cur := 0
  	for i, x := range diff {
  		cur += x
  		if i >= left && i <= right && cur <= 0 {
  			return false
  		}
  	}
  	return true
  }
  

• function isCovered(ranges: number[][], left: number, right: number): boolean {
      const diff = new Array(52).fill(0);
      for (const [l, r] of ranges) {
          ++diff[l];
          --diff[r + 1];
      }
      let cur = 0;
      for (let i = 0; i < 52; ++i) {
          cur += diff[i];
          if (i >= left && i <= right && cur <= 0) {
              return false;
          }
      }
      return true;
  }
  
  

• /**
   * @param {number[][]} ranges
   * @param {number} left
   * @param {number} right
   * @return {boolean}
   */
  var isCovered = function (ranges, left, right) {
      const diff = new Array(52).fill(0);
      for (const [l, r] of ranges) {
          ++diff[l];
          --diff[r + 1];
      }
      let cur = 0;
      for (let i = 0; i < 52; ++i) {
          cur += diff[i];
          if (i >= left && i <= right && cur <= 0) {
              return false;
          }
      }
      return true;
  };
  
  

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