Problem
Find the position (counting from 0) of the first negative number in the list.
Implement first_negative_index(numbers).
Input
numbers: The list of integers.
Output
Return the index, or -1 if there are no negative numbers.
Constraints
0 ≤ length ≤ 100,000
Examples
Example 1
Input:
numbers = [4, 0, -2, -7]
Expected output:
expected = 2Input:
std::vector<long long> numbers = {4, 0, -2, -7};
Expected output:
long long expected = 2;Input:
long[] numbers = new long[] {4, 0, -2, -7};
Expected output:
long expected = 2;Explanation
-2 at index 2 is the first negative value.
Example 2
Input:
numbers = [1, 2, 3]
Expected output:
expected = -1Input:
std::vector<long long> numbers = {1, 2, 3};
Expected output:
long long expected = -1;Input:
long[] numbers = new long[] {1, 2, 3};
Expected output:
long expected = -1;Explanation
There are no negative numbers, so the answer is -1.
How to approach it
Try on your own first, then open one hint at a time.
Hint 1
You only need the first position where a value is below zero.
Hint 2
Scan from left to right and stop as soon as you find one.
Hint 3
If no negative value appears, be sure to return the missing-case value.
Expected complexity
O(n) time, O(1) extra space
References
This challenge is adapted for CodeUtility. Follow the statement and constraints above.