Question 1
Four employees need to be scheduled for three shifts over three days. The constraints are:
- Each employee works exactly one shift per day
- No employee works the same shift two days in a row
- Alice works Morning shift on Monday
- Bob cannot work Night shift
- Charlie works Evening shift on Tuesday
Who works the Evening shift on Wednesday?
Step-by-step solution:
Table Method with Constraint Elimination:
1. Create a 3D table: Days x Shifts x Employees
2. Apply direct constraints:
- Monday Morning: Alice (fixed)
- Tuesday Evening: Charlie (fixed)
- Bob: Never Night shift (all days)
3. Apply rotation constraint:
- Alice (Morning Mon) cannot be Morning Tue
- Charlie (Evening Tue) cannot be Evening Wed
4. Fill Monday:
- Morning: Alice
- Evening: Charlie (can work evening)
- Night: Diana (Bob can't do night)
5. Fill Tuesday:
- Morning: Bob (Alice can't repeat, Charlie is evening)
- Evening: Charlie (fixed)
- Night: Diana (Bob can't)
6. Fill Wednesday:
- Charlie can't be Evening (was Evening Tue)
- Alice can be Evening (was Morning Mon, okay to shift)
- Answer: Alice works Evening on Wednesday
Key Strategy: Apply fixed constraints first, then use rotation rules to eliminate impossible assignments systematically.
Table Method with Constraint Elimination:
1. Create a 3D table: Days x Shifts x Employees
2. Apply direct constraints:
- Monday Morning: Alice (fixed)
- Tuesday Evening: Charlie (fixed)
- Bob: Never Night shift (all days)
3. Apply rotation constraint:
- Alice (Morning Mon) cannot be Morning Tue
- Charlie (Evening Tue) cannot be Evening Wed
4. Fill Monday:
- Morning: Alice
- Evening: Charlie (can work evening)
- Night: Diana (Bob can't do night)
5. Fill Tuesday:
- Morning: Bob (Alice can't repeat, Charlie is evening)
- Evening: Charlie (fixed)
- Night: Diana (Bob can't)
6. Fill Wednesday:
- Charlie can't be Evening (was Evening Tue)
- Alice can be Evening (was Morning Mon, okay to shift)
- Answer: Alice works Evening on Wednesday
Key Strategy: Apply fixed constraints first, then use rotation rules to eliminate impossible assignments systematically.