Euler circuit determination of mixed graphs of ACM/ICPC-network flow (POJ1637)

Network flow judgment mixed Graph//through the network flow so that the points of the same degree of access possible, otherwise the weight of the impossible//residual network is the number of changes in the direction, that is, n two-way Edge has n times//time:157ms memory:348k# Include <iostream> #include <cstring> #include <cstdio> #include <algorithm> #include <queue    >using namespace std; #define MAXN 205#define INF 0x3f3f3f3fint n,m;int s,t;int dif[maxn];int RES[MAXN][MAXN];    Residual network-Represents the variable direction number int Pre[maxn];bool BFs () {memset (pre,-1,sizeof (pre));    Queue<int> Q; Q.push (s);    Pre[s] = 0;        while (!q.empty ()) {int cur = q.front ();        Q.pop (); for (int i = 1; I <= t; i++) {if (pre[i] = = 1 && res[cur][i]) {Pre                [I] = cur;                if (i = = t) return true;            Q.push (i); }}} return false;}    int EK () {int maxflow = 0;        while (BFS ()) {int mind = INF;        for (int i = t; I! = s; i = pre[i]) mind = min (mind, res[pre[i]][i]); for (int i = t; i = s; i = Pre[i]) {res[pre[i]][i]-= mind;        Res[i][pre[i] + + + mind;    } Maxflow + = mind; } return maxflow;}    int main () {//freopen ("In.txt", "R", stdin);    int T;    scanf ("%d", &t);        while (t--) {memset (dif,0,sizeof (DIF));        memset (res,0,sizeof (res));        scanf ("%d%d", &n, &m);        int total = 0; s = 0;        t = n+1;            for (int i = 0; i < m; i++) {int u,v,t;            scanf ("%d%d%d", &u,&v,&t);   dif[u]++;            dif[v]--;  if (t = = 0) res[u][v] + = 1;        Heavy edge then variable direction +1} bool flag = TRUE; for (int i = 1; I <= n; i++) {if (Dif[i] > 0) {//out many-odd-through source points res[s][i] = dif[                I]/2;            Total + = DIF[I]/2;  } if (Dif[i] < 0) res[i][t] =-DIF[I]/2;                In degrees-give odd-out if (ABS (Dif[i])% 2 = = 1) by meeting point {flag = false;            Break }} (Flag && EK () = = TotAL)?    printf ("possible\n"): printf ("impossible\n"); } return 0;}

Euler circuit determination of mixed graphs of ACM/ICPC-network flow (POJ1637)