28. Valid Mountain Walk
EasyArray
A hiking guide describes a trail by listing the altitude at each checkpoint. A trail is a proper mountain walk if it climbs strictly upward for at least one step, reaches a single peak, and then descends strictly downward for at least one step, never staying level and never going up again after the peak.
Write a method isMountain that takes the array nums of checkpoint altitudes and returns true if the trail is a proper mountain walk, and false otherwise.
Example 1
- Input:
- nums = [1,3,5,4,2]
- Output:
- true
- Explanation:
The altitude rises 1, 3, 5 and then falls 4, 2, so this is a mountain.
Example 2
- Input:
- nums = [1,2,3]
- Output:
- false
- Explanation:
The trail only climbs; it never comes back down, so it is not a mountain.
Constraints
1 ≤ nums.length ≤ 1000
0 ≤ nums[i] ≤ 104
How this problem is judged
- Answers
- Your answer must match exactly. Numbers compare by value, so 2 and 2.0 are equal.
Expected complexity
- Time
- O(n)
- Space
- O(1)