text: class Solution:
      """
      @param nums: an integer array and all positive numbers, no duplicates
      @param target: An integer
      @return: An integer
      """
      def backPackIV(self, nums, target):
          '''
              [2,3,6,7]
              7
               0       4     7
              [1,0,0,0,0,0,0,0]
            2 [1,0,1,0,1,0,1,0]
            3 [1,0,1,1,1,1,1,1]
            6 [1,0,1,1,1,1,2,1]
            7 [1,0,1,1,1,1,2,2]
          '''
  
          dp = [0 for _ in range(target + 1)]
          dp[0] = 1
          for num in nums:
              for j in range(num, target + 1):
                  dp[j] += dp[j - num]
  
          return dp[target]