Given n distinct positive integers, integer k (k <= n) and a number target. Find k numbers where sum is target. Calculate how many solutions there are?

public class Solution {
    /**
     * @param A: an integer array.
     * @param k: a positive integer (k <= length(A))
     * @param target: a integer
     * @return an integer
     */
    public int count = 0;
    public int kSum(int A[], int k, int target) {
        // write your code here
        if (A == null || A.length == 0) return 0;
        
        int[][][] dp = new int[A.length + 1][k + 1][target+1];
        //dp[i][j][k] from i numbers pick j numbers sum to target
        for (int i = 0; i <= A.length; i++) {
            dp[i][0][0] = 1;
        }
        for (int i = 1; i <= A.length; i++) {
            for (int j = 1; j <= k; j++) {
                for (int l = 1; l <= target; l++) {
                    dp[i][j][l] = dp[i-1][j][l];
                    if (A[i-1] <= l) {
                        dp[i][j][l] += dp[i-1][j-1][l-A[i-1]];
                    }
                }
            }
        }
        return dp[A.length][k][target];
    }
}