SPOJ - QUEST4, Max Bipartite Matching

2017/quest4.cpp

+#include <cstdio>
+#include <algorithm>
+#include <cstring>
+#include <queue>
+
+#define MAXN 250
+
+using namespace std;
+
+int visited[ MAXN + 1 ], par[ MAXN + 1 ], flow[ MAXN + 1 ][ MAXN + 1 ], cap[ MAXN + 1 ][ MAXN + 1 ];
+
+bool bfs( int s, int t ) {
+  memset( par, 0, sizeof( par ) );
+  memset( visited, 0, sizeof( visited ) );
+  queue< int > Q;
+  Q.push( s );
+  visited[ s ] = true;
+  par[ s ] = -1;
+  while( !Q.empty() ) {
+    int u = Q.front();
+    Q.pop();
+    for( int i = 0; i < MAXN; i++ ) {
+      if( !visited[ i ] && cap[ u ][ i ] - flow[ u ][ i ] > 0 ) {
+        visited[ i ] = true;
+        par[ i ] = u;
+        Q.push( i );
+      }
+    }
+  }
+  return visited[ t ];
+}
+
+int maxflow( int s, int t ) {
+  int ans = 0;
+  while( bfs( s, t ) ) {
+    int aug = 2500000;
+    for( int i = t; i != s; i = par[ i ] ) {
+      aug = min( aug, cap[ par[ i ] ][ i ] - flow[ par[ i ] ][ i ] );
+    }
+    ans += aug;
+    for( int i = t; i != s; i = par[ i ] ) {
+      flow[ par[ i ] ][ i ] += aug;
+      flow[ i ][ par[ i ] ] -= aug;
+    }
+  }
+  return ans;
+}
+
+int main( void ) {
+  int T;
+  scanf("%d", &T );
+  while( T-- ) {
+    int N, x, y;
+    scanf("%d", &N );
+    for( int i = 1; i <= N; i++ ) {
+      scanf("%d%d", &x, &y );
+      cap[ x ][ y + 120 ] = 1;
+    }
+    for( int i = 0; i < 120; i++ ) {
+      cap[ 240 ][ i ] = 1;
+      cap[ i + 120 ][ 241 ] = 1;
+    }
+    printf("%d\n", maxflow( 240, 241 ) );
+    memset( flow, 0, sizeof( flow ) );
+    memset( cap, 0, sizeof( cap ) );
+  }
+  return 0;
+}