# hw8_sol - Homework 8 Solutions 1 The goal is to fill the...

This preview shows pages 1–2. Sign up to view the full content.

Homework 8 Solutions 1) The goal is to fill the knapsack and maximize the total sum of values of the items packed. Because fractions of items can be added, this problem can be solved with a greedy approach. The basic idea is to balance the value of the item added with the size of the item. The more valuable an item is, the more desirable it will be to add to the knapsack. The value of the item can be computed as the value of the item divided by the size of the item. To solve the fractional knapsack problem, simply calculate the value of each item, sort the items by the value, and then add all of the most valuable, followed by the second most, and so forth. At some point, either the knapsack will be full, in which case the algorithm is done, or there will be no further items to add, or there will be more of some item than there is space in the knapsack. Add the amount of this final item to the knapsack required to fill the knapsack. This solves the fractional knapsack problem with an O(n) scan to calculate the values, an O(n log n) sort, and an O(n) sort giving O(nlogn) time. Algorithm 1 [T] =fracKnapsack ( K, S, V) 1: Input: K (the size of the knapsack), S (an array of size n storing both the sizes and the values of elements being used to fill the knapsack 2: Output: A (a list of items containing the elements used to fill knapsack or a state- ment stating that the knapsack can not be filled 3: begin 4: /* initialize the densities of each element to 0*/ 5: for all elements e do 6: e :densit y = 0; 7: end for 8: /* calculate and store densities of each element */ 9: for all elements e do 10: e :densit y = e :valu e = e :siz e; 11: end for 12: /*Sort the elements with respect to their density in descending order*/ 13: /*you are able to use any fast sorting algorithms you know such as quicksort, or even store them in a heap etc. ..*/ 14: /*Initialize packed to 0, this variable represents how much of the knapsack is al-

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 4

hw8_sol - Homework 8 Solutions 1 The goal is to fill the...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online