cplex求解cwvrp代码

以下是使用CPLEX求解CWVRP问题的Python代码：

import cplex
from cplex.exceptions import CplexError

# 定义问题
problem = cplex.Cplex()

# 添加变量
x = []
for i in range(n):
    for j in range(n):
        if i != j:
            x.append('x' + str(i) + '_' + str(j))
problem.variables.add(names=x)

# 添加约束
for i in range(n):
    c = []
    for j in range(n):
        if i != j:
            c.append(x.index('x' + str(i) + '_' + str(j)))
    problem.linear_constraints.add(lin_expr=[cplex.SparsePair(c, [1] * (n - 1))], senses='E', rhs=[1])

for j in range(1, n):
    c = []
    for i in range(n):
        if i != j:
            c.append(x.index('x' + str(i) + '_' + str(j)))
    problem.linear_constraints.add(lin_expr=[cplex.SparsePair(c, [1] * (n - 1))], senses='E', rhs=[1])

for i in range(n):
    for j in range(n):
        if i != j:
            c = []
            c.append(x.index('x' + str(i) + '_' + str(j)))
            c.append(x.index('x' + str(j) + '_' + str(i)))
            problem.linear_constraints.add(lin_expr=[cplex.SparsePair(c, [1, 1])], senses='L', rhs=[1])

# 添加目标函数
obj = []
for i in range(n):
    for j in range(n):
        if i != j:
            obj.append(d[i][j] * x.index('x' + str(i) + '_' + str(j)))
problem.objective.set_sense(problem.objective.sense.minimize)
problem.objective.set_linear(obj)

# 求解问题
problem.solve()

# 打印结果
print('Objective value:', problem.solution.get_objective_value())
for i in range(n):
    for j in range(n):
        if i != j:
            if problem.solution.get_values(x.index('x' + str(i) + '_' + str(j))) > 0.5:
                print('x' + str(i) + '_' + str(j), '=', problem.solution.get_values(x.index('x' + str(i) + '_' + str(j))))

其中，`n`是城市数量，`d`是城市之间的距离矩阵。约束条件包括每个城市只被访问一次、每个车辆出发和返回都必须在仓库、每个城市的进和出必须相等。目标函数为最小化总行驶距离。