#10193. 「一本通 6.1 例 1」序列的第 k 个数

https://loj.ac/s/1025637

LibreOJ/10193/10193.cpp

@@ -0,0 +1,31 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+const int mod = 200907;
+
+long long binpow(long long a, long long b) {
+    a %= mod;
+    long long res = 1;
+    while (b > 0) {
+        if (b & 1) res = res * a % mod;
+        a = a * a % mod;
+        b >>= 1;
+    }
+    return res;
+}
+
+int main() {
+    int t;
+    cin >> t;
+    while (t--) {
+        long long a, b, c, k;
+        cin >> a >> b >> c >> k;
+        if (b - a == c - b) {
+            cout << (a + (b - a) % mod * (k - 1)) % mod << endl;
+        } else if (b / a == c / b) {
+            cout << a * binpow(b / a, k - 1) % mod << endl;
+        }
+    }
+    return 0;
+}