💼 完璧な座席表：リーダーシップ・サミット問題をGo言語で解く 🔗

func solveImpl(state *State) bool {
	if state.solved {
		return true
	}

	// For the first round, consider all people
	start := 0
	end := state.people

	// From the second round onwards, restrict the search space
	if len(state.res) > 0 {
		start = len(state.table) * state.tableSize
		end = start + state.tableSize
	}

	for person := start; person < end; person++ {
		if !valid(state, person) {
			continue // Skip if this assignment causes a conflict
		}
        
		set(state, person) // Assign the seat
		if solveImpl(state) {
			return true // Success!
		}
		unset(state, person) // Backtrack
	}
	
	return false
}

func valid(state *State, person int) bool {
	// Has this person already been seated in this round?
	if state.usedPerson[person] {
		return false
	}
	
	// Has this person sat with anyone currently at this table before?
	for _, there := range state.table {
		first := min(there, person)
		second := max(there, person)
		
		if state.usedPair[first][second] {
			return false
		}
	}
	
	return true
}

func set(state *State, person int) {
	state.usedPerson[person] = true
	
	// Mark this person as having paired with everyone currently at the table
	for _, there := range state.table {
		first := min(there, person)
		second := max(there, person)
		if _, ok := state.usedPair[first]; !ok {
			state.usedPair[first] = map[int]bool{}
		}
		state.usedPair[first][second] = true
	}
	
	state.table = append(state.table, person)
	
	// Move to next table if full
	if len(state.table) != state.tableSize {
		return
	}
	state.round = append(state.round, state.table)
	state.table = []int{}
	
	// Move to next round if all tables are full
	if len(state.round) != state.numTables {
		return
	}
	state.res = append(state.res, state.round)
	state.round = [][]int{}
	state.usedPeople = append(state.usedPeople, state.usedPerson)
	state.usedPerson = map[int]bool{}
	
	// Check if we are completely done
	if len(state.res) != state.numRounds {
		return
	}
	state.solved = true
}

func unset(state *State, person int) {
	state.solved = false
	
	// If the current table is empty, step back to the previous table
	if len(state.table) == 0 {
		if len(state.round) == 0 {
			last := len(state.res) - 1
			state.round = state.res[last]
			state.res = state.res[:last]
			state.usedPerson = state.usedPeople[last]
			state.usedPeople = state.usedPeople[:last]
		}
		last := len(state.round) - 1
		state.table = state.round[last]
		state.round = state.round[:last]
	}
	
	// Remove the person from the table
	state.table = state.table[:len(state.table)-1]
	
	// Unmark pairings
	for _, there := range state.table {
		first := min(there, person)
		second := max(there, person)
		state.usedPair[first][second] = false
	}
	state.usedPerson[person] = false
}

round 0:
  table 0: 0  1  2  3
  table 1: 4  5  6  7
  table 2: 8  9  10 11
  table 3: 12 13 14 15

round 1:
  table 0: 0  4  8  12
  table 1: 1  5  9  13
  table 2: 2  6  10 14
  table 3: 3  7  11 15

round 2:
  table 0: 0  5  10 15
  table 1: 1  4  11 14
  table 2: 2  7  8  13
  table 3: 3  6  9  12

round 3:
  table 0: 0  6  11 13
  table 1: 1  7  10 12
  table 2: 2  4  9  15
  table 3: 3  5  8  14

round 4:
  table 0: 0  7  9  14
  table 1: 1  6  8  15
  table 2: 2  5  11 12
  table 3: 3  4  10 13