在正确答案里有一段代码没有看懂，求助各位大神帮忙指点一下，代码如下：

                long dp[][] = new long[nums.length + 1][(sum >> 1) + 1];

dp[0][0] = 1;

for (int i = 1; i < dp.length; i++) {

for (int j = 0; j < dp[0].length; j++) {

int cnt = j / vals[i - 1];

for (int k = 0; k <= cnt && k <= nums[i - 1]; k++) {

dp[i][j] += dp[i - 1][j - k * vals[i - 1]];

}

}

}

题目链接：http://exercise.acmcoder.com/online/online_judge_ques?ques_id=3353&konwledgeId=157