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| README.md | ||
Mountains or Valleys
A mountain is an array with exactly one peak.
- All numbers to the left of the peak are increasing.
- All numbers to the right of the peak are decreasing.
- The peak CANNOT be on the boundary.
A valley is an array with exactly one trough.
- All numbers to the left of the trough are decreasing.
- All numbers to the right of the trough are increasing.
- The trough CANNOT be on the boundary.
Some examples of mountains and valleys:
Mountain A: [1, 3, 5, 4, 3, 2] // 5 is the peak
Mountain B: [-1, 0, -1] // 0 is the peak
Mountain B: [-1, -1, 0, -1, -1] // 0 is the peak (plateau on both sides is okay)
Valley A: [10, 9, 8, 7, 2, 3, 4, 5] // 2 is the trough
Valley B: [350, 100, 200, 400, 700] // 100 is the trough
Neither mountains nor valleys:
Landscape A: [1, 2, 3, 2, 4, 1] // 2 peaks (3, 4), not 1
Landscape B: [5, 4, 3, 2, 1] // Peak cannot be a boundary element
Landscape B: [0, -1, -1, 0, -1, -1] // 2 peaks (0)
Based on the rules above, write a function that takes in an array and returns either "mountain", "valley", or "neither".
Examples
LandscapeType([3, 4, 5, 4, 3]) ➞ "mountain"
LandscapeType([9, 7, 3, 1, 2, 4]) ➞ "valley"
LandscapeType([9, 8, 9]) ➞ "valley"
LandscapeType([9, 8, 9, 8]) ➞ "neither"
Notes
- A peak is not exactly the same as the max of an array. The max is a unique number, but an array may have multiple peaks. However, if there exists only one peak in an array, then it is true that the peak = max.
- See comments for a hint.