This problem is a logic puzzle that requires us to determine the arrangement of people in a four-storey building based on a set of given conditions. We need to find the number of floors between U and S.

Understanding the Building Structure

• The building has 4 floors, numbered 1 to 4 from bottom to top.
• Each floor has two flats: Flat 1 (left) and Flat 2 (right).
• There are 8 people: P, Q, R, S, T, U, V, W, with one person in each flat.

Step-by-Step Deduction of Floor Arrangements

Let's analyze each condition to deduce the positions:

1. Condition 4: "P lives on an odd-numbered floor but he does not live on the ground floor." The ground floor is floor 1. Odd floors are 1 and 3. Since P does not live on the ground floor (1), P must live on floor 3.
   • P lives on Floor 3.
2. Condition 1: "R and S live on the same floor but above the floor on which P lives." Since P lives on floor 3, R and S must live on the floor above, which is floor 4.
   • R and S live on Floor 4.
3. Condition 8: "V lives on an even-numbered floor just above Q in the same flat of different floors." This means Floor(V) = Floor(Q) + 1 and Flat(V) = Flat(Q), and Floor(V) is even.
   • Possible pairs for (Floor(Q), Floor(V)): (1, 2) or (3, 4).
4. Condition 2: "Q and R live in the same flat on different floors." This means Flat(Q) = Flat(R).
5. Combining Condition 8 and Condition 2: We know Flat(V) = Flat(Q) and Flat(Q) = Flat(R). Therefore, Flat(V) = Flat(Q) = Flat(R).
6. Now let's test the possibilities from Condition 8:
   • If (Floor(Q), Floor(V)) is (3, 4): This implies Q lives on floor 3 and V lives on floor 4. Since P also lives on floor 3, P and Q are on the same floor (Floor 3). Also, Flat(V) = Flat(Q). Since R lives on floor 4 (from step 2) and in the same flat as Q (Flat(R)=Flat(Q)), it means Flat(R) = Flat(Q). Thus, Flat(V) = Flat(Q) = Flat(R). This implies V and R are on the same floor (Floor 4) and in the same flat, which contradicts the rule that each person lives in a different flat.
   • Therefore, the other possibility must be true: (Floor(Q), Floor(V)) is (1, 2).
   • Q lives on Floor 1.
   • V lives on Floor 2.
   • Flat(V) = Flat(Q).
7. Using Flat information: Since Flat(Q) = Flat(R), and Q is on Floor 1, R must be on Floor 4 in the same flat as Q. Let's assume this is Flat 1.
   • Q lives on Floor 1, Flat 1.
   • V lives on Floor 2, Flat 1 (same flat as Q).
   • R lives on Floor 4, Flat 1.
8. Condition 1 revisited: R and S live on the same floor (4). Since R is in Flat 1, S must be in the other flat on floor 4.
   • S lives on Floor 4, Flat 2.
9. Condition 3: "P and V do not live in the same flat on different floors." V lives on Floor 2, Flat 1. P lives on Floor 3. P cannot live in Flat 1.
   • P lives on Floor 3, Flat 2.
10. Condition 5: "U lives below the floor on which V lives." V lives on Floor 2. U must live on a floor below Floor 2, meaning Floor 1. Q is already in Floor 1, Flat 1.
    • U lives on Floor 1, Flat 2.
11. Condition 6: "W does not live with P on the same floor." P lives on Floor 3. W cannot live on Floor 3. The available flats are Floor 2, Flat 2 and Floor 3, Flat 1. Since W cannot be on Floor 3, W must live on Floor 2, Flat 2.
    • W lives on Floor 2, Flat 2.
12. The remaining person is T, and the remaining flat is Floor 3, Flat 1.
    • T lives on Floor 3, Flat 1.
13. Condition 7: "T does not live to the immediate right of P." P is on Floor 3, Flat 2. T is on Floor 3, Flat 1. T lives to the left of P, not to the right. This condition is satisfied.

Final Arrangement

Based on the deductions, the final arrangement is:

Calculating Floors Between U and S

From the final arrangement:

• U lives on Floor 1.
• S lives on Floor 4.

The floors between Floor 1 and Floor 4 are Floor 2 and Floor 3. There are two floors between U and S.

Mathematically, the number of floors between floor $n_1$ and floor $n_2$ (where $n_2 > n_1$) is $(n_2 - n_1) - 1$.

Number of floors = $(4 - 1) - 1 = 3 - 1 = 2$.