题解 | 【模板】集合操作

import bisect
import sys

L = []

def insertValue(x):
    pos = bisect.bisect_left(L, x)
    if pos >= len(L) or L[pos] != x:
        L.insert(pos, x)

def eraseValue(x):
    pos = bisect.bisect_left(L, x)
    if pos < len(L) and L[pos] == x:
        L.pop(pos)

def xInSet(x):
    pos = bisect.bisect_left(L, x)
    print("YES" if pos < len(L) and L[pos] == x else "NO")

def sizeOfSet():
    print(len(L))

def getPre(x):
    pos = bisect.bisect_left(L, x)
    print(L[pos - 1] if pos > 0 else -1)

def getBack(x):
    pos = bisect.bisect_right(L, x)
    print(L[pos] if pos < len(L) else -1)

def main():
    q = int(sys.stdin.readline())
    for _ in range(q):
        parts = list(map(int, sys.stdin.readline().split()))
        op = parts[0]
        x = parts[1] if len(parts) > 1 else 0
        
        if op == 1:
            insertValue(x)
        elif op == 2:
            eraseValue(x)
        elif op == 3:
            xInSet(x)
        elif op == 4:
            sizeOfSet()
        elif op == 5:
            getPre(x)
        elif op == 6:
            getBack(x)

if __name__ == "__main__":
    main()

这题必须用bisect才能达到时间要求O(nlogn), 本来用set()很方便，但是O(n^2) 用例7超时. 哎 Python。。。

然后用input()也不行，一定要sys.stdin.readline()