Check K Sum

/*
 * Author: Yang Pei
 * Problem: Check K Sum
 * 
 * Note:
 * Given an array of non-negative numbers, check if we could use exactly K elements
 * in the array (each element could only be used once) to get a target sum, we assume
 * that the given target and k is valide. 
 * 
 * Solution:
 * Using dp to solve the problem, dp[i][j] means if we could obtain sum i using j 
 * elements, then dp[i][j] |= dp[i-A[k]][j-1].
 */
import java.util.*;

public class CheckKSum {
    public static boolean kSum(int[] num, int target, int k) {
        int n = num.length;
        boolean[][] dp = new boolean[target+1][k+1];
        dp[0][0] = true;
        for(int i = 0; i < n; i++) {
            for(int j = target; j >= num[i]; j--) {
                for(int p = 1; p <= k; p++) {
                    dp[j][p] |= dp[j-num[i]][p-1];
                }
            }
        }
        return dp[target][k];
    }
    
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        while(scan.hasNext()) {
            int n = scan.nextInt();
            int[] num = new int[n];
            for(int i = 0; i < n; i++) {
                num[i] = scan.nextInt();
            }
            int target = scan.nextInt();
            int k = scan.nextInt();
            System.out.println(kSum(num, target, k));
        }
        scan.close();
    }
}