Algorithms Problems
Knapsack problem
Given N items with weights w1, w2....wn, values v1, v2 ... vn and a knapsack of capacity w. Find the most
valuable subset that fits into the knapsack.
1. Define a solution space having feasible and infeasible solutions in it for the optimization
problem
2. Design an exhaustive search algorithm and derieve the complexity of the algorithm
3. Design a recurrence with its state space tree representation
4. Design a backtracking algorithm using the recurrence and derieve the complexity of the
algorithm
5. Design a greedy algorithm which is optimal but leads to an approximation algorithm
6. Design a branch and bound algorithm using the greedy approach
7. Design a dynamic programming algorithm with some constraints on the weights
Implement and Compare the following algorithms for finding the
Binomial Coefficient
1. Binomial_coeff(n, k, DP):
DP[i,0] and DP[i,i] are initialized to 1. everything is initialized to -1
if(DP[n,k] == -1):
DP[n,k] = BC(n-1, k, DP) + BC(n-1, k-1, DP);
return DP[n,k]
2. Binomial(n,k):
for i <- 0 to n:
for j<- 0 to min(i,k):
if(j == 0 or j == i) DP[i,j] <- 1
else DP[i,j] = DP[i-1, j-1] + DP[i-1, j]
return DP[n,k]
3. Binomial(n, k):
if(n-k<k) k<- n-k
for i<-0 to n:
for j<- max(0, k-(n-i)) to min(i,k):
if(j = 0 or j = i) DP[i mod 2, j] = 1
else DP[i mod 2, j] <- DP[i-1mod 2, j] + DP[i-1 mod 2, j-1]
return DP[n mod 2, k]
BST Problem
We are given a sequence k = <k1, k2, ..., kn> of n distinct keys in sorted order so that k1<k2 ... kn, and
we wish to build a BST from these keys. For each key ki, we have probability pi that a search will be for
ki. Some searches may be for values not in K, and so we also have n+1 dummy keys. d0, d1...dn
representing values not in K. d0 represents all values less than k1. dn represents all values greater than
kn. i = 1,2,...n-1 the dummy key di represents all values between ki and ki+1. For each di, we have a
probability qi that a search will correspond to di. Note that each key ki is an internal node and each
dummy key di is a leaf.
Find a way of constructing an optimal BST of k such that the expectations of the search are minimized.
Return the optimal value.
Eat Cake Problem
Wheatley is at the best party in the world: it has infinitely many cakes. Each cake is a square with an
integer side length(in cm). The party has inifnitely many cakes of every possible integer side length. the
cakes all have the same depth. We only consider their areas.
Wheatley is determined to eat one or more cakes that have a total combined area of exactly N cm. Since
he is health conscious; he wants to eat as few cakes as possible. calculate the minimum number of
cakes.
Permutation Game
After a long day, Alice and Bob decided to play a little game. The game board consists of n cells in a
straight line numbered from 1 to n, where each cell contains a number ai between 1 and n.
Furthermore, no two cells can contain the same number.
A token is placed in one of the cells. They take alternating turns in moving the token around the board
with Alice moving first. The current
player can move from cell i to cell j only if the following conditions are satisfied.
1. the number on cell j is strictly greater than the number on cell i
2. the distance that the token travels must be a multiple of the number on the old cell (j-i mod
ai =0)
Whoever is unable to make a move loses. For each possible starting point, determine who wins the
game. Show that this is finite.