algo/maxcut: možnost záporných hran mezi sousedními vrcholy

Implementace pomocí toho, že k celé matici sousednosti přičtu konstantu
a pak odčítám.

algo/maxcut.cpp

@@ -40,7 +40,7 @@ void calc_maxcut_naive(Nd * nd, int nd_size)
 	}
 }
 
-void calc_maxcut_gw(Nd * nd, int nd_size)
+void calc_maxcut_gw(Nd * nd, int nd_size, bool negative_near=false)
 {
 	int thread_num = 4;
 	char cmd[1000];
@@ -52,6 +52,15 @@ void calc_maxcut_gw(Nd * nd, int nd_size)
 			for(auto [target, weight] : nd[i].edges)
 				matrix[i][target-nd] += weight;
 
+		if(negative_near)
+		{
+			fo(i, nd_size) fo(j, nd_size) matrix[i][j] *= 2;
+			fo(i, nd_size) fo(j, nd_size) matrix[i][j]++;
+			fo(i, nd_size-1) matrix[i][i+1]--;
+			fo(i, nd_size-1) matrix[i+1][i]--;
+			fo(i, nd_size) matrix[i][i] = 0;
+		}
+
 		fprintf(p_stdin,
 				"import LinearAlgebra;\
 				import LinearAlgebra;\
@@ -100,6 +109,8 @@ void calc_maxcut(Nd * nd, int nd_size, const char * algorithm)
 	if(!strcmp("naive", algorithm)) calc_maxcut_naive(nd, nd_size);
 	else
 	if(!strcmp("gw", algorithm)) calc_maxcut_gw(nd, nd_size);
+	else
+	if(!strcmp("gw-negative-near", algorithm)) calc_maxcut_gw(nd, nd_size, true);
 	else assert(false);
 }