b=1 k=[[1,1],[1,2],[2,1]] for i in range(n): c=[] if a==1 and sum(k[-1])==sum(k[-2]): a=a b=b+1 c.append(a) c.append(b) k.append(c) elif b==1 and sum(k[-1])==sum(k[-2]): a=a+1 b=b c.append(a) c.append(b) k.append(c) elif k[-1][0]==k[-1][1]: a=a b=b+1 c.append(a) c.append(b) k.append(c) elif a>b: while a!=1: c=[] a=a-1 b=b+1 c.append(a) c.append(b) k.append(c) elif a<b: while b!=1: c=[] a=a+1 b=b-1 c.append(a) c.append(b) k.append(c) print('{}/{}'.format(k[n-1][0],k[n-1][1])) #可以输出答案，为啥不能通过？