Generate permutations

211108_3.py

class Permutation():
    def __init__(self, n):
        self.n = n
        self.a = [None] + [i for i in range(1, self.n+1)]

    def __str__(self):
        return ''.join([str(x) for x in self.a[1:]])

    def final(self):
        return self.a == [None] + [i for i in range(self.n, 0, -1)]
    
    def to_next(self):
        j = self.n - 1
        while self.a[j] >= self.a[j+1]:
            j -= 1

        min = None
        saved_k = None
        for k in range(j+1, self.n+1):
            if self.a[k]>self.a[j] and (min is None or self.a[k]<min):
                saved_k = k
            
        self.a[j], self.a[saved_k] = self.a[saved_k], self.a[j]

        self.a = [self.a[i] for i in range(j+1)] + \
                 list(reversed([self.a[i] for i in range(j+1, self.n+1)]))

    

def generate(n=4):
    curr_config = Permutation(n)
    print(curr_config)
    while True:
        if not curr_config.final():
            curr_config.to_next()
            print(curr_config)
        else:
            break
        
        
generate(n=4)