377. Combination Sum IV

 

思想： dp

状态转移方程：dp[i]=Σdp[i-nums[k]]  0<=k<=nums.length 

代码： 

public class Solution {
    public int combinationSum4(int[] nums, int target) {
        int len = nums.length;
        int[]dp = new int[target+1];
        dp[0]=1;
        Arrays.sort(nums);
        for(int i =0;i<=target;i++){
            for(int num: nums){
                if(i<num)
                    break;
                dp[i] = dp[i]+dp[i-num];    
            }
        }
        return dp[target];
    }
}