【CF】304 E. Soldier and Traveling

基础网络流，增加s和t，同时对于每个结点分裂为流入结点和流出结点。EK求最大流，判断最大流是否等于当前总人数。

 /* 304E */
 #include <iostream>
 #include <string>
 #include <map>
 #include <queue>
 #include <set>
 #include <stack>
 #include <vector>
 #include <deque>
 #include <algorithm>
 #include <cstdio>
 #include <cmath>
 #include <ctime>
 #include <cstring>
 #include <climits>
 #include <cctype>
 #include <cassert>
 #include <functional>
 using namespace std;
 //#pragma comment(linker,"/STACK:102400000,1024000")

 #define rep(i, a, n)     for (int i=a;i<n;++i)
 #define per(i, a, n)     for (int i=n-1;i>=a;--i)
 #define pb                 push_back
 #define mp                 make_pair
 #define all(x)             (x).begin(),(x).end()
 #define SZ(x)             ((int)(x).size())
 #define lson            l, mid, rt<<1
 #define rson            mid+1, r, rt<<1|1

 const int maxn = ;
 int F[maxn][maxn];
 int P[maxn], a[maxn];
 bool visit[maxn];
 int ans[maxn][maxn];
 int ai[maxn], bi[maxn], ci[maxn];
 int n, m, s = , t;
 bool flag = true;

 bool bfs() {
     int u, v;
     queue<int> Q;

     memset(a, , sizeof(a));
     a[s] = INT_MAX;
     Q.push(s);
     P[s] = s;

     while (!Q.empty()) {
         u = Q.front();
         Q.pop();
         for (v=; v<=t; ++v) {
             if (!a[v] && F[u][v]) {
                 P[v] = u;
                 Q.push(v);
                 a[v] = min(a[u], F[u][v]);
             }
         }
     }

     return a[t]==;
 }

 int Edmonds_Karp() {
     int u, v;
     int ans = ;

     while () {
         if (bfs())
             break;
         for (u=t,v=P[u]; u!=s; u=v, v=P[u]) {
             F[u][v] += a[t];
             F[v][u] -= a[t];
         }
         ans += a[t];
     }
     return ans;
 }

 int main() {
     int i, j, k;
     int s1, s2;

     #ifndef ONLINE_JUDGE
         freopen("data.in", "r", stdin);
         freopen("data.out", "w", stdout);
     #endif

     scanf("%d %d", &n, &m);
     t = n+n+;
     memset(F, , sizeof(F));
     memset(ans, , sizeof(ans));
     s1 = s2 = ;

     for (i=; i<=n; ++i) {
         scanf("%d", &ai[i]);
         s1 += ai[i];
         F[][i] = ai[i];
     }

     for (i=; i<=n; ++i) {
         scanf("%d", &bi[i]);
         s2 += bi[i];
         F[i][i+n] = INT_MAX;
         F[i+n][t] = bi[i];
     }

     for (i=; i<m; ++i) {
         scanf("%d %d", &j, &k);
         F[j][k+n] = INT_MAX;
         F[k][j+n] = INT_MAX;
     }

     flag = s1==s2;
     if (flag) {
         flag = Edmonds_Karp() == s1;
     }

     if (flag) {
         for (i=; i<=n; ++i)
             for (j=n+; j<t; ++j)
                 ans[i][j-n] = F[j][i];
         puts("YES");
         for (i=; i<=n; ++i) {
             for (j=; j<=n; ++j)
                 printf("%d ", ans[i][j]);
             putchar('\n');
         }
     } else {
         puts("NO");
     }

     #ifndef ONLINE_JUDGE
         printf("time = %d.\n", (int)clock());
     #endif

     return ;
 }