'commit'

TangDou/AcWing_TiGao/T5/JuZhengChengFa/1303.cpp

@@ -0,0 +1,33 @@
+#include <bits/stdc++.h>
+using namespace std;
+#define int long long
+#define endl "\n"
+const int N = 3;
+int n, mod;
+
+// 矩阵乘法
+void mul(int a[][N], int b[][N], int c[][N]) {
+    int t[N][N] = {0};
+    for (int i = 0; i < N; i++) {
+        for (int j = 0; j < N; j++)
+            for (int k = 0; k < N; k++)
+                t[i][j] = (t[i][j] + (a[i][k] * b[k][j]) % mod) % mod;
+    }
+    memcpy(c, t, sizeof t);
+}
+
+signed main() {
+    int b[N][N] = {1, 1, 1};
+    int m[N][N] = {
+        {1, 0, 0},
+        {1, 1, 1},
+        {0, 1, 0}};
+
+    cin >> n >> mod;
+    // 矩阵快速幂
+    for (int i = n - 1; i; i >>= 1) {
+        if (i & 1) mul(b, m, b);
+        mul(m, m, m);
+    }
+    printf("%d\n", b[0][0]);
+}