Submission #10,793

2024-04-13 14:06:23

python3

Accepted 100/100

625ms

102468 KiB

from sys import stdin
input=stdin.readline

def main():
    N = int(input())
    T = [int(x) for x in input().split()]
    graph={}
    for i in range(N//2):
        j=N-1-i
        if T[i] != T[j]:
            try: graph[T[i]].add(T[j])
            except: graph[T[i]]={T[j]}
            try: graph[T[j]].add(T[i])
            except: graph[T[j]]={T[i]}
    comp=[]
    while graph:
        x,cur = graph.popitem()
        c={x}
        #print(x,cur)
        while cur:
            v=cur.pop()
            new=graph.pop(v)
            c.add(v)
            for v in new:
                if v not in c:
                    cur.add(v)
        comp.append(c.copy())
    #print(comp)
    #print(graph)
    print(sum([len(c)-1 for c in comp]))
    for c in comp:
        lista=list(c)
        lista.sort()
        for i in range(1,len(lista)):
            print(lista[i],lista[0])
        
main()

	Sum	Test	Verdict	Time	Memory
subtask1	0/0
		1	Accepted	17ms	11376 KiB
		2	Accepted	224ms	60204 KiB
subtask2	9/9
		3	Accepted	18ms	12108 KiB
		4	Accepted	18ms	12416 KiB
		5	Accepted	18ms	12492 KiB
		6	Accepted	18ms	12644 KiB
		7	Accepted	18ms	12880 KiB
subtask3	14/14
		8	Accepted	17ms	12856 KiB
		9	Accepted	17ms	12672 KiB
		10	Accepted	17ms	12776 KiB
		11	Accepted	17ms	12828 KiB
		12	Accepted	17ms	12812 KiB
		13	Accepted	17ms	13156 KiB
subtask4	25/25
		14	Accepted	18ms	13324 KiB
		15	Accepted	19ms	13928 KiB
		16	Accepted	23ms	14756 KiB
		17	Accepted	24ms	14940 KiB
		18	Accepted	21ms	15084 KiB
		19	Accepted	21ms	14512 KiB
		20	Accepted	21ms	14560 KiB
		21	Accepted	18ms	14000 KiB
subtask5	22/22
		22	Accepted	351ms	88904 KiB
		23	Accepted	372ms	88592 KiB
		24	Accepted	374ms	88608 KiB
		25	Accepted	351ms	88696 KiB
		26	Accepted	351ms	89172 KiB
		27	Accepted	377ms	89604 KiB
		28	Accepted	377ms	89796 KiB
		29	Accepted	351ms	88824 KiB
		30	Accepted	351ms	88596 KiB
		31	Accepted	377ms	95436 KiB
		32	Accepted	374ms	95448 KiB
		33	Accepted	349ms	88740 KiB
		34	Accepted	389ms	88928 KiB
		35	Accepted	391ms	97844 KiB
		36	Accepted	419ms	98136 KiB
		37	Accepted	388ms	89432 KiB
subtask6	30/30
		38	Accepted	17ms	14384 KiB
		39	Accepted	224ms	62848 KiB
		40	Accepted	18ms	12108 KiB
		41	Accepted	18ms	12416 KiB
		42	Accepted	18ms	12492 KiB
		43	Accepted	18ms	12644 KiB
		44	Accepted	18ms	12880 KiB
		45	Accepted	17ms	12856 KiB
		46	Accepted	17ms	12672 KiB
		47	Accepted	17ms	12776 KiB
		48	Accepted	17ms	12828 KiB
		49	Accepted	17ms	12812 KiB
		50	Accepted	17ms	13156 KiB
		51	Accepted	18ms	13324 KiB
		52	Accepted	19ms	13928 KiB
		53	Accepted	23ms	14756 KiB
		54	Accepted	24ms	14940 KiB
		55	Accepted	21ms	15084 KiB
		56	Accepted	21ms	14512 KiB
		57	Accepted	21ms	14560 KiB
		58	Accepted	18ms	14000 KiB
		59	Accepted	351ms	88904 KiB
		60	Accepted	372ms	88592 KiB
		61	Accepted	374ms	88608 KiB
		62	Accepted	351ms	88696 KiB
		63	Accepted	351ms	89172 KiB
		64	Accepted	377ms	89604 KiB
		65	Accepted	377ms	89796 KiB
		66	Accepted	351ms	88824 KiB
		67	Accepted	351ms	88596 KiB
		68	Accepted	377ms	95436 KiB
		69	Accepted	374ms	95448 KiB
		70	Accepted	349ms	88740 KiB
		71	Accepted	389ms	88928 KiB
		72	Accepted	391ms	97844 KiB
		73	Accepted	419ms	98136 KiB
		74	Accepted	388ms	89432 KiB
		75	Accepted	538ms	102200 KiB
		76	Accepted	352ms	87612 KiB
		77	Accepted	181ms	57736 KiB
		78	Accepted	356ms	87692 KiB
		79	Accepted	279ms	62912 KiB
		80	Accepted	104ms	57964 KiB
		81	Accepted	112ms	58236 KiB
		82	Accepted	107ms	58180 KiB
		83	Accepted	625ms	102468 KiB
		84	Accepted	174ms	58336 KiB
		85	Accepted	261ms	63184 KiB
		86	Accepted	108ms	58216 KiB
		87	Accepted	108ms	58172 KiB
		88	Accepted	111ms	58124 KiB
		89	Accepted	108ms	58160 KiB