package algorithm.leetcode;

import java.util.Arrays;

/**
 * @author: mayuan
 * @desc: 组合总和 Ⅳ
 * @date: 2018/08/23
 */
public class Solution377 {
    public int combinationSum4(int[] nums, int target) {
        if (nums == null || nums.length == 0) {
            return 0;
        }

        // dp[i]表示:和为i的组合的个数
        int[] dp = new int[target + 1];
        dp[0] = 1;
        Arrays.sort(nums);

        for (int i = 1; i <= target; ++i) {
            for (int j = 0; j < nums.length && nums[j] <= i; ++j) {
                dp[i] += dp[i - nums[j]];
            }
        }
        return dp[target];
    }
}