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最新推荐文章于 2025-10-06 18:43:01 发布

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文章讲述了如何用Python实现贪心策略解决AtCoder中的C-AttackSurvival、E-WhoSaysaPun?和F-XorSum3问题，涉及堆操作、字符串哈希和线性基计算。

C - Attack Survival
遍历
D - Powerful Discount Tickets
堆贪心，每次操作都在最大的那一个，然后重新插入

# -*- coding: utf-8 -*-
# @time     : 2023/6/2 13:30
# @author   : yhdu@tongwoo.cn
# @desc     :
# @file     : atcoder.py
# @software : PyCharm
import bisect
import copy
import sys
from sortedcontainers import SortedList
from collections import defaultdict, Counter, deque
from functools import lru_cache, cmp_to_key
import heapq
import math
sys.setrecursionlimit(50005)


def main():
    items = sys.version.split()
    if items[0] == '3.10.6':
        fp = open("in.txt")
    else:
        fp = sys.stdin
    n, m = map(int, fp.readline().split())
    a = list(map(int, fp.readline().split()))
    qu = [-x for x in a]
    heapq.heapify(qu)
    while qu and m:
        x = -heapq.heappop(qu)
        heapq.heappush(qu, -(x >> 1))
        m -= 1
    ans = 0
    for x in qu:
        ans -= x
    print(ans)


if __name__ == "__main__":
    main()

E - Who Says a Pun?
字符串hash
C++提交了几次都没有过，反而是pypy一次通过

# -*- coding: utf-8 -*-
# @time     : 2023/6/2 13:30
# @author   : yhdu@tongwoo.cn
# @desc     :
# @file     : atcoder.py
# @software : PyCharm
import bisect
import copy
import sys
from sortedcontainers import SortedList
from collections import defaultdict, Counter, deque
from functools import lru_cache, cmp_to_key
import heapq
import math
sys.setrecursionlimit(5005)


def check(s, t, n):
    for i in range(n):
        if s[i] != t[i]:
            return False
    return True


def main():
    items = sys.version.split()
    if items[0] == '3.10.6':
        fp = open("in.txt")
    else:
        fp = sys.stdin

    def dig(c):
        return ord(c) - ord('a') + 1

    n = int(fp.readline())
    s = fp.readline().strip()
    mod = 10 ** 9 + 7

    p = 131
    hp = 1
    ans = 0
    for l in range(1, n // 2 + 1):
        temp = 0
        pos_dict = dict()
        for i in range(l):
            temp = (temp * p + dig(s[i])) % mod
        pos_dict[temp] = l - 1
        for i in range(l, n):
            temp = (temp - hp * dig(s[i - l])) % mod
            temp = (temp * p + dig(s[i])) % mod
            if temp in pos_dict:
                last = pos_dict[temp]
                if last < i - l + 1 and check(s[last - l + 1: last + 1], s[i - l + 1: i + 1], l):
                    ans = max(ans, l)
                    break
            else:
                pos_dict[temp] = i
        hp = hp * p % mod
    print(ans)


if __name__ == "__main__":
    main()

F - Xor Sum 3

线性基
不能在线性基中贪心地选取最大异或和

# -*- coding: utf-8 -*-
# @time     : 2023/6/2 13:30
# @author   : yhdu@tongwoo.cn
# @desc     :
# @file     : atcoder.py
# @software : PyCharm
import bisect
import copy
import sys
from sortedcontainers import SortedList
from collections import defaultdict, Counter, deque
from functools import lru_cache, cmp_to_key
import heapq
import math
sys.setrecursionlimit(5005)


def main():
    items = sys.version.split()
    if items[0] == '3.10.6':
        fp = open("in.txt")
    else:
        fp = sys.stdin
    p = [0] * 64
    n = int(fp.readline())
    a = list(map(int, fp.readline().split()))

    def insert(x):
        for i in range(63, -1, -1):
            if (x >> i) & 1:
                if p[i] == 0:
                    p[i] = x
                    return 1
                else:
                    x ^= p[i]
        return 0

    s = 0
    for t in a:
        s ^= t
    for i in range(64):
        if (s >> i) & 1:
            for j in range(n):
                if (a[j] >> i) & 1:
                    a[j] ^= 1 << i

    for t in a:
        insert(t)
    ans1 = 0
    for i in range(63, -1, -1):
        if ans1 ^ p[i] > ans1:
            ans1 = ans1 ^ p[i]
    ans2 = s ^ ans1
    print(ans1 + ans2)


if __name__ == "__main__":
    main()