nums.dp with size r + 1 and set dp[0] to 1.dp to a new array pSum for prefix sum processing.
b. Update pSum by adding pSum[i - num] to pSum[i] for each i from num to r.
c. Update dp using the prefix sums, considering the frequency of the current element.dp[i] for i from l to r.10^9 + 7.