Problem Statement
 
You are given a int[] f that describes a set of values from a function f. The x-th element (zero-indexed) is the value of f(x). The function is not convex at a particular x value if there exist y and z values such that y < x < z, and the point (x, f(x)) lies strictly above the line between points (y, f(y)) and (z, f(z)) in the Cartesian plane. All x, y, and z values must be between 0 and n-1, inclusive, where n is the number of elements in f. Return the number of places where f is not convex.
Definition
 
Class:
ConvexityIssues
Method:
howMany
Parameters:
int[]
Returns:
int
Method signature:
int howMany(int[] values)
(be sure your method is public)
 

Constraints
-
f will contain between 3 and 50 elements, inclusive.
-
Each element of f will be between -1000 and 1000, inclusive.
Examples
0)

 
{0,1,4,9,16,25}
Returns: 0
The function is convex at all given points.
1)

 
{0,2,2}
Returns: 1
The point (1,2) is not below the line from (0,0) to (2,2).
2)

 
{1, 2, 3, 4, 5, 6, 7, 8}
Returns: 0

3)

 
{-1000, -501, 0, 500, 1000}
Returns: 2

4)

 
{-1000, 1, 1000}
Returns: 1


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我名到是报了,就是那天一直在上课,没参加.(其实本来我实力就还不行,所以参不参加也无所谓了,呵呵:)