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You are given a convex polygon P on n vertices in the plane (specified by their x and y coordinates). A triangulation of P is a collection of n-3diagonals of such that no two diagonals intersect (except possibly at their endpoints). Notice that a triangulation splits the polygon鈥檚 interior into n-2 disjoint triangles. The cost of a triangulation is the sum of the lengths of the diagonals in it. Give an efficient algorithm for finding a triangulation of minimum cost. (Hint: Label the vertices of P by 1,....,n, starting from an arbitrary vertex and walking clockwise. For 1i<jn, let the subproblem A(i,j)denote the minimum cost triangulation of the polygon spanned by vertices i,i+1,...,j.).

Short Answer

Expert verified

Convex Polygon: A convex polygon is a close figure whose each interior angle is less than 180This means that no diagonal can be made which passes outside the boundary of polygon.

Step by step solution

01

Defining the Recursive Equation of Minimum Cost Triangulation

We will make our recursive equation in such a way that no diagonal cross eachother. For numbering, we will follow clockwise direction.

If Ai,jdenote minimum cost triangulation, where i,jare different vertices, Then i,i=0as we cannot make diagonal using same vertice.

Thus, Recursive Equation is:

localid="1657271470951" Ai,j=0minikjAi,k+Ak,j+di,k+dk,j0;ifi=j

Now it is important to define the length of diagonal(d). It is given as:

di,j=xi-xj2+yi-yj220;otherwise;ifj-i2

02

Implementing Algorithm

The algorithm would be as follows:

fori=0tonAi,j=0form=1ton-1fori=1ton-mj=i+mminikjAi,j+Ak,j+di,k+dk,j

returnA1,n

03

Analyse the Algorithm

Now, the outer for loop takes0ntime to compute each of the entry ofAi,j

The two nested loop takes 0n2time. So the effective time complexity will be0n3.

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