分支限界法求解旅行商，C语言代码，用伪代码对算法进行描述

分支限界法是一种用于解决组合优化问题，如旅行商问题（Traveling Salesman Problem，TSP）的有效算法。它通过系统地生成并剪枝搜索树来寻找最优解决方案。以下是旅行商问题的简单分支限界算法的伪代码描述：

// Pseudocode for Branch and Bound algorithm for TSP

function tsp_bracket_bound(city_list, current_city, best_distance):
    if current_city == last_city: // base case: all cities visited
        return best_distance

    unvisited_cities = city_list - {current_city} // remaining cities to visit
    best_distance_so_far = infinity // initialize with a large value
    open_nodes = PriorityQueue() // contains nodes to explore
    open_nodes.enqueue((0, [current_city], current_city)) // start from current city

    while open_nodes is not empty:
        distance, path, current_city = open_nodes.dequeue()
        
        if distance + distance_to_next_city(current_city, next_city) < best_distance_so_far:
            best_distance_so_far = distance
            new_path = path + [next_city] // add the next city to the path
            open_nodes.enqueue((distance + distance_to_next_city(next_city, unvisited_cities[0]), new_path, unvisited_cities[0]))

        if distance >= best_distance:
            break // prune the branch if it cannot improve the solution

    return best_distance_so_far

// Distance function (assuming euclidean distance)
function distance_to_next_city(city1, city2):
    // Calculate distance between two cities here

main():
    city_list = ... // list of cities
    best_tour_length = tsp_bracket_bound(city_list, city_list[0], 0)
    print("Best tour length:", best_tour_length)