hdu2444二分图判定 ＋ 最大匹配

思路：用染色法进行二分图判定，相邻的两个点间染不同的颜色，如果遇见相同的颜色，则不是二分图；

不是二分图的话输出No，否则跑Hungary求最大匹配；

点击打开链接

/*****************************************Author      :Crazy_AC(JamesQi)Time        :2015File Name   :*****************************************/// #pragma comment(linker, "/STACK:1024000000,1024000000")#include <iostream>#include <algorithm>#include <iomanip>#include <sstream>#include <string>#include <stack>#include <queue>#include <deque>#include <vector>#include <map>#include <set>#include <stdio.h>#include <string.h>#include <math.h>#include <stdlib.h>#include <limits.h>using namespace std;#define MEM(a,b) memset(a,b,sizeof a)#define pk push_backtemplate<class T> inline T Get_Max(const T&a,const T&b){return a < b?b:a;}template<class T> inline T Get_Min(const T&a,const T&b){return a < b?a:b;}typedef long long ll;typedef pair<int,int> ii;const int inf = 1 << 30;const int INF = 0x3f3f3f3f;const int MOD = 1e9 + 7;int uN,vN,n,m;const int maxn = 220;int gg[maxn][maxn];bool vis[maxn];int link[maxn];bool dfs(int u){for (int i = 0;i < vN;i++){if (gg[u][i] && !vis[i]){vis[i] = true;if (link[i] == -1 || dfs(link[i])){link[i] = u;return true;}}}return false;}inline int Hungary(){MEM(link, -1);int ret = 0;for (int i = 0;i < uN;++i){MEM(vis, false);if (dfs(i)) ret++;}return ret;}int color[maxn];vector<int> vec[maxn];bool SetColor(int u,int col){color[u] = col;for (int i = 0;i < vec[u].size();++i){int v = vec[u][i];if (color[v] != -1){if (color[v] == col) return false;continue;}if (!SetColor(v, !col)) return false;}return true;}int num[maxn];int main(){// ios::sync_with_stdio(false);// freopen("in.txt","r",stdin);// freopen("out.txt","w",stdout);while(~scanf("%d%d",&n,&m)){for (int i = 0;i < n;++i)vec[i].clear();int u,v;while(m--){scanf("%d%d",&u,&v);u--,v--;vec[u].push_back(v);}MEM(color, -1);bool flag = true;for (int i = 0;i < n;++i){if (color[i] != -1) continue;if (!SetColor(i,0)){flag = false;break;}}if (!flag){printf("No\n");continue;}vN = uN = 0;for (int i = 0;i < n;++i){if (color[i] == 0) num[i] = uN++;else num[i] = vN++;}MEM(gg, 0);for (int i = 0;i < n;++i){for (int j = 0;j < vec[i].size();j++){if (color[i] == 0){u = num[i];v = num[vec[i][j]];gg[u][v] = 1;}else{u = num[vec[i][j]];v = num[i];gg[u][v] = 1;}}}printf("%d\n",Hungary());}return 0;}