题目链接:Codeforces 385E Bear in the Field
题目大意:有一片n*n的草莓地,每个位置的初始草莓量为横坐标和纵坐标的和,然后每过一秒增长一个草莓。然后给出熊的初始位置(sx,sy),以及移动的速度(dx,dy),每一秒发生的事:(1)速度增加k(k为该位置的草莓数);(2)熊的位置发生移动;(3)每个位置上草莓数+1
解题思路:矩阵快速幂,根据题目给出的条件,先让坐标从0~n-1.然后输出时+1即可。
sx[t] = sx[t-1] + dx[t-1] + k = sx[t-1] + dx[t-1] + sx[t-1] + sy[t-1] + t-1 + 2(因为坐标为0~n-1)
sy[t] = sy[t-1] + dy[t-1] + k = sy[t-1] + dy[t-1] + sx[t-1] + sy[t-1] + t-1 + 2
dx[t] = dx[t-1] + sx[t-1] + sy[t-1] + t-1 + 2
dy[t] = dy[t-1] + sx[t-1] + sy[t-1] + t-1 + 2
t = t-1 + 1
所以就可以写出矩阵
2 1 1 0 1 2
1 2 0 1 1 2
1 1 1 0 1 2
1 1 0 1 1 2
0 0 0 0 1 1
0 0 0 0 0 1
#include <stdio.h> #include <string.h> #include <iostream> using namespace std; typedef long long ll; const int N = 10; ll n, sx, sy, dx, dy, t; struct mat { int r, c; ll k[N][N]; void init(int r, int c) { this->r = r; this->c = c; memset(k, 0, sizeof(k)); } void clear() { //memset(k, 0, sizeof(k)); k[0][0] = k[0][5] = k[1][1] = k[1][5] = k[2][5] = k[3][5] = 2; k[0][1] = k[0][2] = k[0][4] = k[1][0] = k[1][3] = k[1][4] = k[2][0] = k[2][1] = k[2][2] = k[2][4] = 1; k[3][0] = k[3][1] = k[3][3] = k[3][4] = k[4][4] = k[4][5] = k[5][5] = 1; } friend mat operator * (const mat& a, const mat& b) { mat ans; ans.init(a.r, b.c); for (int i = 0; i < ans.r; i++) { for (int j = 0; j < ans.c; j++) { for (int x = 0; x < b.r; x++) ans.k[i][j] = ((ans.k[i][j] + a.k[i][x] * b.k[x][j]) % n + n) % n; } } return ans; } }; int main() { cin >> n >> sx >> sy >> dx >> dy >> t; mat ans; ans.init(6, 1); ans.k[0][0] = sx - 1; ans.k[1][0] = sy - 1; ans.k[2][0] = dx; ans.k[3][0] = dy; ans.k[4][0] = 0; ans.k[5][0] = 1; mat b; b.init(6, 6); b.clear(); while (t) { if (t&1) ans = b * ans; b = b * b; t>>=1; } cout << ans.k[0][0] + 1 << " " << ans.k[1][0] + 1 << endl; return 0; }