Overview

Given \(N\) days of temperature data \(T_1, T_2, \dots, T_N\), the problem asks you to count how many days have temperatures that fall within a specified range \([L, R]\) (i.e., at least \(L\) ℃ and at most \(R\) ℃).

Analysis

What this problem requires is determining whether each day’s temperature \(T_i\) satisfies the following condition: - \(L \leq T_i \leq R\)

The maximum value of \(N\) is \(10^5\). If we take a straightforward approach (simulation) of checking each day one by one to see if the condition is met, we can find the answer with a total of \(N\) checks. Since a computer can perform tens of millions to hundreds of millions of calculations per second, for processing on the order of \(N=10^5\), this method is more than sufficient to obtain a correct answer (AC) well within the time limit.

Algorithm

The problem can be solved with the following steps:

1. Initialize a variable ans to \(0\) for counting the number of days.
2. Repeat the following process for \(i = 1\) to \(N\):
   • Read the temperature \(T_i\) for day \(i\).
   • If \(L \leq T_i\) and \(T_i \leq R\), increment ans by \(1\).
3. Output the final value of ans.

Complexity

• Time complexity: \(O(N)\)
  • Since we check each temperature data entry exactly once, the time required is proportional to the number of data entries \(N\).
• Space complexity: \(O(N)\)
  • In this implementation, we use sys.stdin.read().split() to store all input data in a list at once, so the memory usage is proportional to the input size.

Implementation Notes

• Efficient input: Since \(N\) can be as large as \(10^5\), calling input() \(N\) times in Python may result in long execution times. By using sys.stdin.read().split(), all data can be read from standard input at once, enabling faster processing.

• Writing range checks: In Python, you can chain comparison operators like L <= temp <= R. This has the same meaning as writing L <= temp and temp <= R, resulting in intuitive and concise code.

  Source Code

import sys

def solve():
    # 標準入力からすべてのデータを読み込み、空白や改行で分割する
    input_data = sys.stdin.read().split()
    if not input_data:
        return
    
    # 最初の3つの値を取得
    N = int(input_data[0])
    L = int(input_data[1])
    R = int(input_data[2])
    
    # 残りのN個の気温データを取得
    T = map(int, input_data[3:])
    
    # 条件を満たす日数をカウント
    ans = 0
    for temp in T:
        if L <= temp <= R:
            ans += 1
            
    # 結果を出力
    print(ans)

if __name__ == "__main__":
    solve()

This editorial was generated by gemini-3-flash-thinking.