hdu 2817

模拟。

#include "iostream"
#include "algorithm"
#include "cstring"

#define int long long
#define d(x) cerr << #x << " => " << x << endl
#define dd(x) cerr << #x << endl
#define D cerr << "Passed [" << __FUNCTION__ << "] on line " << __LINE__ << endl
#define ms(x) memset(x, 0, sizeof x)
using namespace std;

int rd() {
    int f = 1, val = 0; int ch = getchar();
    while(!isdigit(ch)) f = (ch == '-' ? -1 : 1), ch = getchar();
    while(isdigit(ch)) val = val * 10 + ch - '0', ch = getchar();
    return f * val;
}

const int mod = 200907;

int qpow(int a, int b) {
  int res = 1, base = a % mod;
  while(b) {
    if(b & 1) res = res * base % mod;
    base = base * base % mod; b >>= 1;
  }
  return res % mod;
}

int positive(int x) {
    return (x % mod + mod) % mod;
}

void solve() {
    int a = rd(), b = rd(), c = rd(), k = rd();
    if(b - a == c - b) {
        int d = positive(b - a); 
        cout << positive(a + d % mod * (k - 1) % mod) << endl;
    } else {
        int q = b / a % mod;
        cout << a * qpow(q, k - 1) % mod << endl;
    }
}

signed main() {
    int T = rd();
    while(T--) solve();
    return 0;
}

hdu 2818

带权并查集。