Topcoder SRM 358: SharksDinner

Some sharks want dinner, and they want to eat each other. Each pair has a size, speed, and intelligence. Shark A can eat shark B and enter the size, speed, and intelligence of A to be greater than or equal to shark B. In addition, each shark can eat a maximum of two other sharks.
Given int [] Size, Int [] SpeedAnd int [] IntelligenceThe minimum number of sharks that survive.

Analysis: the minimum number of sharks that survive is required, and the maximum number of sharks to be eaten is required.
Suppose there are n sharks. We create a bipartite graph. Each shark has 3 Ax1, Ax2, and Bx vertices. Ax1 and Ax2 are in the left graph of the Bipartite Graph, in the right corner of the Bipartite Graph, if shark x can eat shark y, we create an edge Ax1-> By, Ax2->, the problem is converted to finding the maximum matching match of the Bipartite Graph. The final result is n-match.
The maximum matching of a bipartite graph uses the Hungary algorithm (search for augmented path)

Code: # Include <iostream>
# Include <vector>
Using namespace std;

Struct st {
Int a [3];
St (){
For (int I = 0; I <3; I ++) a [I] = 0;
}
St (int A, int B, int C ){
A [0] =;
A [1] = B;
A [2] = C;
}
};

Const int MAXN = 250;

Bool eq (const st & x, const st & y ){
For (int I = 0; I <3; I ++)
If (x. a [I]! = Y. a [I])
Return false;
}

// Judge whether shark x can eat shark y
Bool can_eat (const st & x, const & y ){
If (eq (x, y) return false;
For (int I = 0; I <3; I ++)
If (x. a [I] <y. a [I]) return false;
Return true;
}

St a [MAXN]; // saves shark Information
Bool gr [MAXN] [MAXN]; // Bipartite Graph
Int n, m; // number of nodes in two subgraphs
Int match [MAXN]; // records the matching information of a bipartite graph.
Bool us [MAXN]; // records whether the node in the second subgraph of the bipartite graph has been used

// Search for the augmented path from the v node in the first subgraph of the Bipartite Graph
Bool go (int v ){
For (int I = 0; I <m; I ++ ){
If (us [I]) continue;
If (gr [v] [I]) {
If (match [I] =-1 ){
Us [I] = 1;
Match [I] = v;
Return true;
}
}
}
For (int I = 0; I <m; I ++ ){
If (us [I]) continue;
If (gr [v] [I]) {
Us [I] = 1;
If (go (match [I]) {
Match [I] = v;
Return true;
}
}
}
Return false;
}

// Perform the maximum binary match
Int matcher (){
Int res = 0;
Memset (match, 255, sizeof match );

// Perform the n-path addition operation
For (int I = 0; I <n; I ++ ){
Memset (us, 0, sizeof us );
If (go (I) ++ res;
}
Return res;
}

Class SharksDinner {
Public:
Static int min1_vors (vector <int> A, vector <int> B, vector <int> C ){
N = A. size ();
Memset (gr, 0, sizeof (gr ));
For (int I = 0; I <n; I ++)
A [I] = st (A [I], B [I], C [I]);

// Construct a Bipartite Graph
For (int I = 0; I <n; I ++ ){
For (int j = 0; j <n; j ++ ){
If (can_eat (a [I], a [j]) {
Gr [2 * I] [j] = 1;
Gr [2 * I + 1] [j] = 1;
}
}
For (int j = 0; j <I; j ++ ){
If (eq (a [I], a [j]) {
Gr [2 * I] [j] = 1;
Gr [2 * I + 1] [j] = 1;
}
}
}
N = 2 * A. size ();
M = A. size ();
Return m-matcher ();
}
};