拓扑排序bfs_dfs

Posted 2021-01-11 cgjh

 

dfs

#include <cstdio>
#include <cstring>
using namespace std;

const int maxn = 1e5+50;
struct Edge{
    int lst;
    int to;
}edge[maxn*5];
int head[maxn];

int qsz;

inline void add(int u, int v) {
    edge[qsz].lst = head[u];
    edge[qsz].to  = v;
    head[u] = qsz++;
}

int vis[maxn];
int  ans[maxn];
int qtot;
bool dfs(int u) {
    int v, i;
    vis[u] = -1;
    for (i=head[u]; i; i=edge[i].lst) {
        v = edge[i].to;
        if (vis[v] == -1) return false;
        else if (!vis[v] && !dfs(v)) return false;
    }
    ans[qtot--] = u; 
    vis[u] = 1;    
    return true;
}

int main()
{
    int t, n, m, i, j, u, v;
    scanf("%d", &t);
    while (t--) {
        // init;
        qsz = 1;
        memset(head, 0, sizeof(head));
        memset( vis, 0, sizeof( vis));
        scanf("%d%d", &n, &m);
        qtot = n;
        for (i=1; i<=m; ++i) {
            scanf("%d%d", &u, &v);
            add(v, u);
        }
        for (i=1; i<=n; ++i) 
            if (!vis[i]) 
                if (!dfs(i)) 
                    break;
                    
        if (!qtot) printf("Correct
");
        else printf("Wrong
");
    }
    
    return 0;
}

 

bfs

#include <cstdio>
#include <cstring>
using namespace std;

const int maxn = 1e5+50;
struct Edge{
    int lst;
    int to;
}edge[maxn*5];
int head[maxn];
int qsz;


int inq[maxn];
int q[maxn];
int qhead;
inline void add(int u, int v) {
    edge[qsz].lst = head[u];
    edge[qsz].to  = v;
    head[u] = qsz++;
}

int main()
{
    int t, n, m, i, j, u, v;
    scanf("%d", &t);
    while (t--) {
        // init;
        qsz = 1;
        memset(head, 0, sizeof(head));
        memset(inq,  0, sizeof( inq));
        qhead = 0;
        
        scanf("%d%d", &n, &m);
        for (i=1; i<=m; ++i) {
            scanf("%d%d", &u, &v);
            add(u, v);
            inq[v]++;
        }
        for (i=1; i<=n; ++i) 
            if (!inq[i]) 
                q[qhead++] = i;
        for (i=0; i<qhead; ++i) {
            for (j=head[q[i]]; j; j=edge[j].lst) {
                v = edge[j].to;
                inq[v]--;
                if (!inq[v]) q[qhead++] = v;
            }
        }
        if (qhead == n) printf("Correct
");
        else printf("Wrong
");
    }
    
    return 0;
}