dp of size n+1 with all elements set to 0, except dp[0] which is set to 1 (base case: one way to build a house with 0 cards).n.i, iterate backwards through the dp array from n down to i.j in the iteration, update dp[j] by adding dp[j-i] to it. This represents the number of ways to build the remaining structure with j-i cards after using i cards for the current row.dp[n] which represents the number of ways to build a house of cards using exactly n cards.