POJ 1753 Flip Game (Dfs+ enumeration)

POJ 1753

Test instructions

Enter a 4*4 image, consisting of black and white color, define an operation: Change the color of a small ball in a lattice (black to white, white to black), while its top and bottom around the lattice inside the ball will also change color. The minimum number of operations can make it a solid color pattern.

Ideas:

For a lattice operation an even number of times equals no operation, the operation odd number of times equals the operation once, so the answer is between 0~16 and impossible.

Starting from N=0 enumeration of the possible composition of n operations, that is, the operation of which lattice, if a certain combination can change the pattern to a solid color will stop.

Because the total number of combinations reaches 2^16, enumeration combinations can be traced back by DFS.

Another method is the bitwise operation +BFS, the details can be referenced http://www.cnblogs.com/lyy289065406/archive/2011/07/29/2120501.html

Code

/** @author novicer* language:c++/c*/#include <iostream> #include <sstream> #include <fstream># include<vector> #include <list> #include <deque> #include <queue> #include <stack># include<map> #include <set> #include <bitset> #include <algorithm> #include <cstdio># include<cstdlib> #include <cstring> #include <cctype> #include <cmath> #include <ctime># Include<iomanip> #define INF 2147483647#define CLS (x) memset (x,0,sizeof (x)) #define RISE (I,A,B) for (int i = A; I < = b; i++) using namespace Std;const double eps (1e-8); typedef long LONG lint;int map[6][6] = {};int flag = 0, Step;int change_r Ow[] = {0,-1,0,1,0};int change_col[] = {0,0,1,0,-1};bool All_color () {for (int i = 1; I <= 4; i++) for (int j = 1; J &lt ; = 4; J + +) if (map[i][j]! = map[1][1]) return False;return true;} void Flip (int row, int col) {for (int i = 0; i < 5; i++) map[row+change_row[i]][col+change_col[i]] =! map[row+change_row[i]][col+Change_col[i]];} void Dfs (int row, int col, int deep) {if (deep = = Step) {flag = All_color (); return;} if (flag) return;if (Row > 4 | | col > 4) Return;flip (Row,col), if (Row < 4) Dfs (row+1, col, deep+1); Elsedfs (1, col+1, deep+1); Flip (Row,col); if (Row < 4) Dfs (row+1, col, deep); Elsedfs (1, col+1, deep); return;} void input () {for (int i = 1, i <= 4; i++) for (int j = 1; J <= 4; j + +) {char c;cin >> C; MAP[I][J] = (c = = ' B ')? 1:0;}} void Solve () {for (step = 0; step <=, step++) {DFS (1,1,0); if (flag) break;} if (flag) cout << step << endl;elsecout << "impossible" << Endl;} int main () {//freopen ("Input.txt", "R", stdin),//freopen ("Output.txt", "w+", stdout); input (); solve (); return 0;}

Copyright notice: Bo Master said authorized all reproduced:)

POJ 1753 Flip Game (Dfs+ enumeration)