题目描述

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样例

#include<bits/stdc++.h>

using namespace std;

int months[13] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

bool check(int r){
    int year = r / 10000;
    int month = r % 10000 / 100;
    int day = r % 100;

    if (!month || month >= 13 || !day) return false;
    if (month != 2 && day > months[month]) return false;
    if (month == 2){
        bool leap = year % 4 == 0 && year % 100 != 0 || year % 400 == 0;
        if (day > 28 + leap) return false;
    }
    return true;
}

int main(){

    int date1, date2;
    cin >> date1 >> date2;

    int res = 0;

    //构造、枚举回文日期
    for (int i = 1000; i < 10000; i ++ ){
        int r = i , x = i;
        for (int j = 0; j < 4; j ++ ){
            r = r * 10 + x % 10;
            x = x / 10;
        }
        if (r >= date1 && r <= date2 && check(r)) res ++ ;
    }
    printf("%d",res);

    return 0;
}
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算法1

(暴力枚举) $O(n^2)$

blablabla

时间复杂度

参考文献

C++ 代码

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算法2

(暴力枚举) $O(n^2)$

blablabla

时间复杂度

参考文献

C++ 代码

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