Problem:
0-1 Knapsack Problem II

You have N items that you want to put them into a knapsack. Item i has value vi and weight wi.

You want to find a subset of items to put such that:

The total value of the items is as large as possible.

The items have combined weight at most W, that is capacity of the knapsack.

Find the maximum total value of items in the knapsack.

Input

N W
v1 w1
v2 w2
:
vN wN

The first line consists of the integers N and W. In the following N lines, the value and weight of the i-th item are given.

Output

Print the maximum total values of the items in a line.

Constraints

1 ≤ N ≤ 100

1 ≤ vi ≤ 100

1 ≤ wi ≤ 10,000,000

1 ≤ W ≤ 1,000,000,000

Sample Input 1

4 5
4 2
5 2
2 1
8 3

Sample Output 1

13

Sample Input 2

2 20
5 9
4 10

Sample Output 2

9

Solution in JAVA (judge verdict: Wrong Answer)

import java.util.*;

public class Main {
	static int items;
	static int max;
	static int[] value;
	static int[] cost;
	static HashMap<Integer, Integer> map = new HashMap<>();

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		items = sc.nextInt();
		max = sc.nextInt();
		value = new int[items];
		cost = new int[items];

		for (int i = 0; i < items; i++) {
			int a = sc.nextInt();
			int b = sc.nextInt();
			value[i] = a;
			cost[i] = b;
		}
		System.out.println(compute(max, items - 1));
	}

	public static int compute(int limit, int pos) {

		if (limit < 0) {
			return Integer.MIN_VALUE / 2;
		}
		if (limit == 0 || pos < 0) {
			return 0;
		}
		try {
			if (map.get(Integer.hashCode(limit + pos)+Integer.hashCode(limit * pos)) != null) {
				return map.get(Integer.hashCode(limit + pos)+Integer.hashCode(limit * pos));
			}
		} catch (Exception e) {
		}

		int include = value[pos] + compute(limit - cost[pos], pos - 1);
		int exclude = compute(limit, pos - 1);
		int a = Integer.hashCode(limit + pos) + Integer.hashCode(limit * pos);
		map.put(a, Math.max(include, exclude));
		return Math.max(include, exclude);
	}
}