D. Good Trip

合集 - codeforces(57)

1.C. Insert and Equalize2023-12-062.C. Removal of Unattractive Pairs2023-12-063.D. Jumping Through Segments2023-12-084.E. Good Triples2023-12-085.F. Shift and Reverse2023-12-086.D. Yet Another Monster Fight2023-12-117.A. Constructive Problems2023-12-188.C. Game with Multiset2023-12-199.A. Rating Increase2023-12-1910.B. Swap and Delete2023-12-1911.A. Problemsolving Log2023-12-2012.B. Preparing for the Contest2023-12-2013.C. Quests2023-12-2014.D. Three Activities2023-12-2015.E2. Game with Marbles (Hard Version)2023-12-2016.cf刷题有感2023-12-2017.A. Anonymous Informant2023-12-2118.A. Forked!2023-12-2319.B. Make Almost Equal With Mod2023-12-2720.C. Heavy Intervals2023-12-2721.D. Split Plus K2023-12-2822.A. 20232023-12-3123.B. Two Divisors2023-12-3124.C. Training Before the Olympiad2023-12-3125.D. Mathematical Problem2024-01-0226.F. Greetings2024-01-0227.C. Partitioning the Array2024-01-1528.G. Bicycles2024-01-1629.E. Eat the Chip2024-01-1730.G. Lights2024-01-1731.D. Array Repetition2024-01-1732.D. Berserk Monsters2024-01-2233.E. Increasing Subsequences2024-01-2334.D. Very Different Array2024-01-2435.G. Mischievous Shooter2024-01-2536.B. Plus-Minus Split2024-01-2737.B. A Balanced Problemset2024-01-2838.C. Did We Get Everything Covered2024-01-2839.D. Find the Different Ones!2024-02-0840.C. Grouping Increases2024-02-10

41.D. Good Trip2024-02-12

42.C. Physical Education Lesson2024-02-1243.E. Final Countdown2024-02-1844.D. Divisible Pairs2024-02-1945.G. Vlad and Trouble at MIT2024-02-2046.A. Brick Wall2024-02-2847.B. Minimize Inversions2024-02-2848.C. XOR-distance2024-02-2849.A. Moving Chips2024-02-2850.B. Monsters Attack!2024-02-2851.C. Find B2024-02-2852.D. Slimes2024-02-2853.C. Turtle Fingers: Count the Values of k2024-02-2854.D. Turtle Tenacity: Continual Mods2024-02-2855.D. Vlad and Division2024-02-2856.C. LR-remainders2024-02-2857.D. Lonely Mountain Dungeons2024-03-12

收起

原题链接

题解

1.把分数中的除法用乘以逆元表示，在求模运算里的除法都可以用乘以逆元代替（如果除法的结果为整数），但是这里规定了可以用其表示，那就用其表示
2.读题

code

#include<bits/stdc++.h>
int mod=1e9+7; // 确保 mod 是一个整数
using namespace std;

// 快速幂函数，计算 base 的 exponent 次幂，模 mod
long long qpow(long long base, long long exponent, long long mod) {
    long long result = 1;
    base = base % mod; // 确保 base 小于 mod
    while (exponent > 0) {
        if (exponent % 2 == 1) {
            result = (result * base) % mod;
        }
        base = (base * base) % mod;
        exponent >>= 1; // exponent /= 2
    }
    return result;
}

int main() {
    int t;
    cin >> t;
    while (t--) {
        int n, m, k;
        long long sum = 0; // 使用长整型避免潜在的溢出
        cin >> n >> m >> k;
        for (int i = 1; i <= m; i++) {
            int x, y;
            long long z; // 使用长整型避免潜在的溢出
            cin >> x >> y >> z;
            sum = (sum + z) % mod;
        }

        long long p = (long long)n * (n - 1) % mod; // 使用长整型避免潜在的溢出
        long long ans = 0;
        p = 2 * qpow(p, mod - 2, mod) % mod; // 使用 qpow 计算逆元
        while (k--) {
            ans = (ans + sum * p % mod) % mod;
            sum = (sum + m * p % mod) % mod;
        }
        cout << ans << endl;
    }
    return 0;
}