added new sample files
added argument verificztion
created Knapstack interface
Revert "created Knapstack interface"

This reverts commit 3bb7010e9a3793706b25632ab55fca5e57ff254e.
created Knapsack interface
created KnaspsackDP - dynamic programming implementation
created Item class for Knapstack problem
Revert "created Item class for Knapstack problem"

This reverts commit 5fc0e8780b027ebc5edc04d17449c361415bbb41.
Revert "Revert "created Item class for Knapstack problem""

This reverts commit 616dae8204dbdead4a6a7d4c0aa52ea4bf71802a.
small fix