algoadvance

Given an integer array arr, return true if there are three consecutive odd numbers in the array. Otherwise, return false.

Example 1:

Input: arr = [2,6,4,1]
Output: false
Explanation: There are no three consecutive odds.

Example 2:

Input: arr = [1,3,5,7]
Output: true
Explanation: [1, 3, 5] are three consecutive odds.

Example 3:

Input: arr = [1, 2, 34, 3, 4, 5, 7, 23, 12]
Output: true
Explanation: [5, 7, 23] are three consecutive odds.

Clarifying Questions

1. Is the input array always non-empty?
2. What is the size range of the input array?
3. Can the input array contain negative numbers?

Assuming general constraints of LeetCode problems:

• The input array can have a length of up to ( 10^4 ).
• The elements of the array can be large and might include negative numbers.

Strategy

1. Traverse through the array while checking each number to see if it is odd.
2. Maintain a counter that counts consecutive odd numbers.
3. Reset the counter to zero whenever an even number is encountered.
4. If the counter reaches 3 at any point, return true.
5. If the entire array is traversed and no three consecutive odd numbers are found, return false.

Code

Let’s implement this strategy in Python.

def three_consecutive_odds(arr):
    count = 0
    for num in arr:
        if num % 2 != 0:  # Check if the number is odd
            count += 1
            if count == 3:
                return True
        else:
            count = 0  # Reset the counter if the number is even
    return False

# Test examples
print(three_consecutive_odds([2,6,4,1]))  # Output: False
print(three_consecutive_odds([1,3,5,7]))  # Output: True
print(three_consecutive_odds([1, 2, 34, 3, 4, 5, 7, 23, 12]))  # Output: True

Time Complexity

• Time Complexity: ( O(n) ), where ( n ) is the length of the input array. This is because we are traversing the array only once.
• Space Complexity: ( O(1) ), as we are using a constant amount of extra space (only a few integer variables).

This solution efficiently checks for three consecutive odd numbers in the array within linear time.

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