HDU 1269 Maze Castle (strong Unicom component, Tarjan algorithm)

Problem Description:

To train Gardon's sense of direction, he built a large castle with N rooms (n<=10000) and M-Lanes (m<=100000), each of which is unidirectional, that is, if a passage is said to be connected to room A and room B, It is only possible to reach room B through this passage from room A, but it does not mean that it can be reached by Room B via it. Gardon need to ask you to write a procedure to confirm whether any two rooms are interconnected, namely: for arbitrary I and J, there is at least one path can be from room I to room J, there is a path can be from room J to room I.

Input:

The input contains more than one set of data, the first line of input has two numbers: N and M, and the next m row has two numbers a and B, indicating that a passage can come from room A to room B. The file ends with two 0.

Output:

For each set of data entered, if any two rooms are connected to each other, output "Yes", otherwise output "No".

Sample Input:

3 31 22 33 13 31 22 33 20 0

Sample Output:

Yes
No

#include <iostream> #include <cstring> #include <cstdlib> #include <cstdio> #include <cmath > #include <vector> #include <queue> #include <stack> #include <set> #include <map># Define LL long longusing namespace Std;const int maxn = 10000 + 10;vector<int>g[maxn];int PRE[MAXN], LOWLINK[MAXN], SCCNO[MAXN], Dfs_clock, scc_cnt;//scc_cnt as the strong Unicom component counter, Sccno[i] represents the strong Unicom component number where node I resides. stack<int>s;void dfs (int u) {pre[u    ] = Lowlink[u] = ++dfs_clock;    S.push (U);        for (int i=0;i<g[u].size (); i++) {int v = g[u][i];            if (!pre[v]) {DFS (v);        Lowlink[u] = min (Lowlink[u], lowlink[v]);        } else if (!sccno[v]) {Lowlink[u] = min (Lowlink[u], pre[v]);        }} if (lowlink[u] = = Pre[u]) {scc_cnt++;        for (;;) {int x = S.top ();            S.pop ();            SCCNO[X] = scc_cnt;        if (x = = u) break; }}}void Tarjan (int n) {Dfs_clocK = scc_cnt = 0;    memset (sccno, 0, sizeof (SCCNO));    memset (pre, 0, sizeof (pre)); for (int i=1;i<=n;i++) if (!pre[i]) DFS (i);}    int main () {int n, m;        while (scanf ("%d%d", &n, &m)!=eof) {if (n = = 0 && m = = 0) break;        int u, v;        for (int i=0;i<=n;i++) g[i].clear ();            for (int i=0;i<m;i++) {scanf ("%d%d", &u, &v);        G[u].push_back (v);        } tarjan (n); //If the number of strong unicom components is 1, it proves that all points are strongly connected if (scc_cnt = = 1) printf ("yes\n");    else printf ("no\n"); } return 0;}

HDU 1269 Maze Castle (strong Unicom component, Tarjan algorithm)