【HDOJ】2444 The Accomodation of Students

图论的题目。着色原理+二分图匹配。

 #include <cstdio>
 #include <cstring>

 #define MAXN 205

 char map[MAXN][MAXN];
 int link[MAXN];
 int color[MAXN];
 bool visit[MAXN];
 int n, m;

 bool dfs(int v, int col) {
     int i;

     for (i=; i<=n; ++i) {
         if (map[i][v]) {
             if (color[i] == col)
                 return false;
             else if (color[i] == ) {
                 color[i] = -col;
                 if (dfs(i, -col) == false)
                     return false;
             }
         }
     }
     return true;
 }

 bool find(int v) {
     int i;

     for (i=; i<=n; ++i) {
         if (!visit[i] && map[i][v]) {
             visit[i] = true;
             if (link[i]== || find(link[i])) {
                 link[i] = v;
                 return true;
             }
         }
     }
     return false;
 }

 int main() {
     int ans;
     int i, j;

     while (scanf("%d%d", &n, &m) != EOF) {
         memset(map, , sizeof(map));
         memset(link, , sizeof(link));
         memset(color, , sizeof(color));
         while (m--) {
             scanf("%d %d", &i, &j);
             map[i][j] = map[j][i] = ;
         }
         color[] = ;
         if (dfs(, ) == false) {
             printf("No\n");
             continue;
         }
         for (ans=, i=; i<=n; ++i) {
             memset(visit, false, sizeof(visit));
             if (find(i))
                 ++ans;
         }
         printf("%d\n", ans/);
     }

     return ;
 }