P2017 [Usaco09dec] halo ox Dizzy Cows

Graph theory everyday does not series ...

Test instructions: Given directed and non-directed edges, and then directed to each non-directional edge, so that the resulting graph is not ring.

I wanted to shrink a little bit, but the more I wanted to faint.

Then he turned the puzzle and suddenly ...

In fact, only need to give a picture of the edge to run once toposort. The orientation of the non-directional side is then considered to be the addition of a directed edge.

Obviously do not violate the topological order to add a forward edge, this diagram can not have a ring!

So just do it.

Code:

#include <cstdio> #include <queue>const int maxn = 100005;struct edges{int next, to;} E[MAXN * 3];int Head[ma XN], tot;int indegree[maxn];int TOPO[MAXN], ttot;int where[maxn];struct query{int u, v;}    Q[maxn];int N, M1, M2;int read () {int ans = 0, s = 1;    char ch = getchar ();    while (Ch > ' 9 ' | | ch < ' 0 ') {if (ch = = '-') s =-1; ch = GetChar ();}    while (Ch >= ' 0 ' && ch <= ' 9 ') ans = (ans << 3) + (ans << 1) + CH-' 0 ', ch = getchar (); return s * ans;}    void link (int u, int v) {E[++tot] = (Edges) {Head[u], v}; Head[u] = tot;}    void Toposort () {std::queue<int> q;    for (int i = 1; I <= n; i++) if (indegree[i] = = 0) Q.push (i);        while (!q.empty ()) {int u = q.front (); Q.pop ();        Topo[++ttot] = u;            for (int i = head[u]; i; i = e[i].next) {int v = e[i].to;            indegree[v]--;            if (indegree[v] = = 0) {Q.push (v); }}}}int Main() {n = read (), m1 = Read (), M2 = read ();        while (m1--) {int u = read (), V = read ();        Link (u, v);    indegree[v]++;            } for (int i = 1; I <= m2; i++) {q[i].u = Read (), Q[I].V = Read ();    } toposort ();    for (int i = 1; I <= ttot; i++) where[topo[i]] = i;        for (int i = 1; I <= m2; i++) {int temp1 = where[q[i].u], temp2 = where[q[i].v];        if (Temp1 < TEMP2) printf ("%d%d\n", q[i].u, Q[I].V);    else printf ("%d%d\n", Q[I].V, q[i].u); } return 0;}

P2017 [Usaco09dec] halo ox Dizzy Cows