Hdu4998rotate (matrix transformation)

Hdu4998rotate (matrix transformation)

You are required to rotate a Graph P around a vertex every time. After rotating it n times, you are required to ask which vertex the graph can rotate at a time.

Solution: each rotation is equivalent to a matrix transformation. After N rotations, the system performs n matrix transformations. Finally, the rotation points and degrees are reversed based on the final matrix. Because cos (R) = 0 may occur, the atan2 function will not cause errors.

The matrix transformation of rotating P around a certain point

Code:

# Include <cstdio> # include <cstring> # include <cmath> using namespace STD; const int n = 15; const double Pi = ACOs (-1.0 ); struct rec {Double V [3] [3]; Rec () {memset (v, 0, sizeof (v);} void Init (double CX, double cy, double R) {v [0] [0] = cos (r); V [0] [1] = sin (R ); V [1] [0] =-sin (r); V [1] [1] = cos (R ); V [2] [0] = Cx-cx * Cos (r) + cy * sin (r); V [2] [1] = cy-cx * sin (r) -Cy * Cos (r); V [2] [2] = 1;} rec operator * (const rec & A) {rec TMP; For (INT I = 0; I <3; I ++) for (Int J = 0; j <3; j ++) for (int K = 0; k <3; k ++) TMP. V [I] [J] + = V [I] [k] *. V [k] [J]; return TMP;} rec operator * = (const rec & A) {return * This = * This * A ;}} rec [N]; int main () {int t; int N; Double X, Y, R; scanf ("% d", & T); While (t --) {scanf ("% d", & N); For (INT I = 0; I <n; I ++) {scanf ("% lf ", & X, & Y, & R); REC [I]. init (X, Y, R);} rec ans = rec [0]; for (INT I = 1; I <n; I ++) ans * = rec [I]; r = atan2 (ans. V [0] [1], ans. V [0] [0]); If (r <0) r = 2 * PI + R; double a1 = (1-ans. V [0] [0]); double a2 = ans. V [0] [1]; double b1 = A1; double b2 = a2; Double A = ans. V [2] [0]; Double B = ans. V [2] [1]; y = (A * B2 + B * A1)/(A1 * B1 + A2 * B2); X = (b1 * Y-B) /B2; printf ("%. 10lf %. 10lf %. 10lf \ n ", X, Y, R);} return 0 ;}

Hdu4998rotate (matrix transformation)