洛谷题单入门4-P5728 【深基5.例5】旗鼓相当的对手-python

输入格式

第一行一个正整数 N。

接下来 N 行，每行三个整数，其中第 i 行表示第 i 名同学的语文、数学、英语成绩。最先读入的同学编号为 1。

输出格式

输出一个整数，表示“旗鼓相当的对手”的对数。

说明/提示

数据保证，2≤N≤1000 且每科成绩为不超过 150 的自然数。

遍历

class Solution:
    @staticmethod
    def oi_input():
        """仅读取原始三科成绩"""
        n = int(input())
        students = []
        for _ in range(n):
            ch, ma, en = map(int, input().split())
            students.append((ch, ma, en))
        return n, students

    @staticmethod
    def oi_test():
        """仅提供原始测试数据"""
        return 3, [
            (90, 90, 90),
            (85, 95, 90),
            (80, 100, 91)
        ]

    @staticmethod
    def solution(n, raw_students):
        """包含所有数据处理逻辑"""
        # 预处理：计算总分
        students = [(s[0], s[1], s[2], sum(s)) for s in raw_students]

        count = 0
        for i in range(n):
            for j in range(i + 1, n):
                '''先检查总分 再检查各科'''
                if abs(students[i][3] - students[j][3]) > 10:
                    continue
                if all(abs(students[i][k] - students[j][k]) <= 5 for k in range(3)):
                    count += 1

        print(count)

oi_input = Solution.oi_input
oi_test = Solution.oi_test
solution = Solution.solution

if __name__ == '__main__':
    n, students = oi_test()
    # n, students = oi_input()
    solution(n, students)

哈希

class Solution:
    @staticmethod
    def oi_input():
        """仅读取原始三科成绩"""
        n = int(input())
        students = []
        for _ in range(n):
            ch, ma, en = map(int, input().split())
            students.append((ch, ma, en))
        return n, students

    @staticmethod
    def oi_test():
        """仅提供原始测试数据"""
        return 3, [
            (90, 90, 90),
            (85, 95, 90),
            (80, 100, 91)
        ]

    @staticmethod
    def solution(n, raw_students):
        """包含所有数据处理逻辑"""
        from collections import defaultdict
        # 预处理：计算总分
        students = [(s[0], s[1], s[2], sum(s)) for s in raw_students]

        # 构建总分哈希表 defaultdict 在没有找到值的情况下会，创建空的列表和键 k-v
        total_map = defaultdict(list)
        for idx, s in enumerate(students):
            '''前索引 后s列表'''
            total_map[s[3]].append(idx)

        count = 0
        for i in range(n):
            current_total = students[i][3]
            # 生成有效总分范围
            for t in range(current_total - 10, current_total + 11):
                if t not in total_map:
                    continue
                for j in total_map[t]:
                    '''j > i 防止重复比较'''
                    if j > i and all(abs(students[i][k] - students[j][k]) <= 5 for k in range(3)):
                        count += 1
        print(count)

oi_input = Solution.oi_input
oi_test = Solution.oi_test
solution = Solution.solution

if __name__ == '__main__':
    n, students = oi_test()
    # n, students = oi_input()
    solution(n, students)