Formatted question description: https://leetcode.ca/all/1437.html

1437. Check If All 1’s Are at Least Length K Places Away (Medium)

Given an array nums of 0s and 1s and an integer k, return True if all 1's are at least k places away from each other, otherwise return False.

 

Example 1:

Input: nums = [1,0,0,0,1,0,0,1], k = 2
Output: true
Explanation: Each of the 1s are at least 2 places away from each other.

Example 2:

Input: nums = [1,0,0,1,0,1], k = 2
Output: false
Explanation: The second 1 and third 1 are only one apart from each other.

Example 3:

Input: nums = [1,1,1,1,1], k = 0
Output: true

Example 4:

Input: nums = [0,1,0,1], k = 1
Output: true

 

Constraints:

  • 1 <= nums.length <= 10^5
  • 0 <= k <= nums.length
  • nums[i] is 0 or 1

Related Topics:
Array

Solution 1.

// OJ: https://leetcode.com/problems/check-if-all-1s-are-at-least-length-k-places-away/

// Time: O(N)
// Space: O(1)
class Solution {
public:
    bool kLengthApart(vector<int>& A, int k) {
        int prev = -k - 1;
        for (int i = 0; i < A.size(); ++i) {
            if (A[i] == 0) continue;
            if (i - prev <= k) return false;  
            prev = i;
        }
        return true;
    }
};

Java

  • class Solution {
        public boolean kLengthApart(int[] nums, int k) {
            if (k == 0)
                return true;
            int length = nums.length;
            int prevOneIndex = -k - 1;
            for (int i = 0; i < length; i++) {
                if (nums[i] == 1) {
                    if (i - prevOneIndex <= k)
                        return false;
                    prevOneIndex = i;
                }
            }
            return true;
        }
    }
    
  • // OJ: https://leetcode.com/problems/check-if-all-1s-are-at-least-length-k-places-away/
    // Time: O(N)
    // Space: O(1)
    class Solution {
    public:
        bool kLengthApart(vector<int>& A, int k) {
            int prev = -k - 1;
            for (int i = 0; i < A.size(); ++i) {
                if (A[i] == 0) continue;
                if (i - prev <= k) return false;  
                prev = i;
            }
            return true;
        }
    };
    
  • class Solution(object):
        def kLengthApart(self, nums, k):
            """
            :type nums: List[int]
            :type k: int
            :rtype: bool
            """
            left_1 = float("-inf")
            for i, num in enumerate(nums):
                if num == 1:
                    if i - left_1 < k + 1:
                        return False
                    left_1 = i
            return True
    

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