Leetcode每日一题 —— 2409. 统计共同度过的日子数

魔法师 2026-10-24 08:04 1

思路

简单题简单做，朴素思路，直接换算成一年中的第几天，然后就好算了。

代码

class Solution {

    private static final int[] days = new int[] { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

    public int countDaysTogether(String arriveAlice, String leaveAlice, String arriveBob, String leaveBob) {

        int arriveA = dayInYear(arriveAlice);

        int leaveA = dayInYear(leaveAlice);

        int arriveB = dayInYear(arriveBob);

        int leaveB = dayInYear(leaveBob);

        int ans = Math.min(leaveA, leaveB) - Math.max(arriveA, arriveB) + 1;

        return ans > 0 ? ans : 0;

    }

    private int dayInYear(String day) {

        int m = Integer.parseInt(day.substring(0, 2));

        int d = Integer.parseInt(day.substring(3, 5));

        int res = 0;

        for (int i = 0; i < m - 1; i++) {

            res += days[i];

        }

        res += d;

        return res;

    }

}

最新回复 (11)

0wFF 10-24 08:05

1楼

这么早的吗w
qidor 10-24 08:07

2楼

早上好啊，顶一下。
tommyjin 10-24 08:11

3楼

求点难题，这也太水了
迷渡 10-24 08:56

4楼

现在 codex 和其他各种 ai 刷题是不是毫无障碍了

Lvvvv 10-24 09:53

5楼

简单题

class Solution {

public:

    int countDaysTogether(string arriveAlice, string leaveAlice, string arriveBob, string leaveBob) {

        vector<int> mon_day = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

        for(int i = 1; i < mon_day.size(); i++) {

            mon_day[i] += mon_day[i - 1];

        }

        auto getval = [&mon_day](string s) -> int {

            int mon = (s[0] - '0') * 10 + s[1] - '0';

            int day = (s[3] - '0') * 10 + s[4] - '0';

            return mon_day[mon - 1] + day;

        };

        int al = getval(arriveAlice), ar = getval(leaveAlice);

        int bl = getval(arriveBob), br = getval(leaveBob);

        int interl = max(al,bl), interr = min(ar,br);

        return max(0,interr - interl + 1);

    }

};

SomeBottle 10-24 10:05

6楼

全转换为天数再计算区间交叠。

class Solution {

public:

    int countDaysTogether(string arriveAlice, string leaveAlice, string arriveBob, string leaveBob) {

        // 本质天数计算题

        // 先生成前缀和

        int days[]={31,59,90,120,151,181,212,243,273,304,334,365};

        // 先全转换为天数

        auto toDays=[&](string& arrive)->int {

            int arriveMonth=stoi(arrive.substr(0,2));

            int arriveDay=stoi(arrive.substr(3));

            if(arriveMonth>1){

                arriveDay+=days[arriveMonth-2];

            }

            return arriveDay;

        };

        int arriveA=toDays(arriveAlice),leaveA=toDays(leaveAlice);

        int arriveB=toDays(arriveBob),leaveB=toDays(leaveBob);

        if(arriveB>=arriveA&&arriveB<=leaveA){

            return min(leaveA,leaveB)-arriveB+1;

        }else if(leaveB>=arriveA&&leaveB<=leaveA){

            return leaveB-max(arriveA,arriveB)+1;

        }else if(arriveA>=arriveB&&arriveA<=leaveB){

            return min(leaveA,leaveB)-arriveA+1;

        }else if(leaveA>=arriveB&&leaveA<=leaveB){

            return leaveA-max(arriveA,arriveB)+1;

        }

        return 0;

    }

};

好像写复杂了，用 Go 重新写了一下:

func countDaysTogether(arriveAlice string, leaveAlice string, arriveBob string, leaveBob string) int {

    // 本质天数计算题

    // 先生成前缀和

    days:=[]int{31,59,90,120,151,181,212,243,273,304,334,365}

    // 先全转换为天数

    toDays:=func(arrive string) int {

        arriveMonth,_:=strconv.Atoi(arrive[:2])

        arriveDay,_:=strconv.Atoi(arrive[3:])

        if arriveMonth>1 {

            arriveDay+=days[arriveMonth-2]

        }

        return arriveDay

    }

    arriveA,leaveA:=toDays(arriveAlice),toDays(leaveAlice)

    arriveB,leaveB:=toDays(arriveBob),toDays(leaveBob)

    return max(0,min(leaveA,leaveB)-max(arriveA,arriveB)+1);

}

tiansuohaoer 10-24 10:07

7楼

模拟题

const int p[13]{0,0,31,59,90,120,151,181,212,243,273,304,334};

class Solution {

public:

    int get(string s){

        return p[stoi(s.substr(0,2))]+stoi(s.substr(3));

    }

    int countDaysTogether(string a1, string a2, string b1, string b2) {

        return max(0,min(get(a2),get(b2))-max(get(a1),get(b1))+1);

    }

};

宙读之魔术士 10-24 11:36

8楼

Kotlin每日重拳出击（前缀和+字符串比较）：

class Solution {

    companion object {

        val PREFIX_SUMS = intArrayOf(31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31)

            .runningFold(0, Int::plus)

    }



    fun countDaysTogether(arriveAlice: String, leaveAlice: String, arriveBob: String, leaveBob: String): Int {

        val maxArriveDay = getDayByDate(maxOf(arriveAlice, arriveBob))

        val minLeaveDay = getDayByDate(minOf(leaveAlice, leaveBob))

        return maxOf(minLeaveDay - maxArriveDay + 1, 0)

    }



    private fun getDayByDate(date: String): Int {

        return PREFIX_SUMS[(date[0] - '0') * 10 + (date[1] - '1')] + (date[3] - '0') * 10 + (date[4] - '0')

    }

}

咪帕 10-24 13:25

9楼

朴素解法

class Solution {

public:

    int countDaysTogether(string arriveAlice, string leaveAlice, string arriveBob, string leaveBob) {

        vector<int> days {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

        auto date2days = [&](const string& s) -> int {

            int m = stoi(s.substr(0, 2));

            int d = stoi(s.substr(3, 2));

            return accumulate(days.begin(), days.begin() + m - 1, d);

        };

        pair<int, int> a = {date2days(arriveAlice), date2days(leaveAlice)};

        pair<int, int> b = {date2days(arriveBob), date2days(leaveBob)};

        if (a.first > b.first) swap(a, b);

        if (a.second < b.first) return 0;

        return min(a.second, b.second) - b.first + 1;

    }

};

Qiansui 10-24 13:35

10楼

注意下标捏~

class Solution {

public:

    pair<int, int> parse_string(string ss){

        int m = stoi(ss.substr(0, 2)), d = stoi(ss.substr(3, 2));

        return {m, d};

    }



    int countDaysTogether(string arriveAlice, string leaveAlice, string arriveBob, string leaveBob) {

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

        pair<int, int> aa = parse_string(arriveAlice), la = parse_string(leaveAlice), ab = parse_string(arriveBob), lb = parse_string(leaveBob);

        pair<int, int> st = max(aa, ab), ed = min(la, lb);

        int ans = 0;

        if(st <= ed)

            for(int m = st.first; m <= ed.first; ++ m){

                ans += days[m];

                if(m == st.first) ans -= st.second - 1;

                if(m == ed.first) ans -= days[m] - ed.second;

            }

        return ans;

    }

};

CPython 10-25 16:15

11楼

来补题啦佬友

class Solution:

    def countDaysTogether(self, arriveAlice: str, leaveAlice: str, arriveBob: str, leaveBob: str) -> int:

        m = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

        dd = [0] * 13

        for i in range(1, 13):

            dd[i] += dd[i-1] + m[i-1]

        # dd = [0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365]



        def cc(s):

            mo = int(s[:2])

            da = int(s[3:])

            return dd[mo-1] + da



        aa, ab, la, lb = cc(arriveAlice), cc(arriveBob), cc(leaveAlice), cc(leaveBob)

        if la < ab or lb < aa:

            return 0

        return min(la, lb) - max(aa, ab) + 1

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