HDU4324(拓扑排序)

来源：互联网发布：java实现推荐算法实例编辑：程序博客网时间：2024/05/22 00:05
#include <bits/stdc++.h>using namespace std;#define maxn 2111#define maxm 8111111int t, n;char mp[maxn][maxn];struct node {    int from, to, next;}edge[maxm];int head[maxn];int cnt;bool vis[maxn];int indegree[maxn], outdegree[maxn];void add_edge (int from, int to, int i) {    node &e = edge[i];    e.from = from, e.to = to, e.next = head[from], head[from] = i;}int topo () {    int ans = 0;    queue <int> gg;    while (!gg.empty ())        gg.pop ();    for (int i = 0; i < n; i++) {        if (!indegree[i])            gg.push (i), ans++, vis[i] = 1;    }    while (!gg.empty ()) {        int u = gg.front (); gg.pop ();        for (int i = head[u]; i != -1; i = edge[i].next) {            int v = edge[i].to;            if (vis[v])                continue;            indegree[v]--;            if (!indegree[v])                gg.push (v), ans++, vis[v] = 1;        }    }    return ans;}int main () {    //freopen ("in", "r", stdin);    scanf ("%d", &t);    int kase = 0;    while (t--) {        scanf ("%d", &n);        printf ("Case #%d: ", ++kase);        cnt = 0;        memset (head, -1, sizeof head);        memset (indegree, 0, sizeof indegree);        memset (outdegree, 0, sizeof outdegree);        memset (vis, 0, sizeof vis);        for (int i = 0; i < n; i++) {            scanf ("%s", mp[i]);        }        for (int i = 0; i < n; i++) {            for (int j = 0; j < n; j++) {                if (mp[i][j] == '1') {                    add_edge (i, j, cnt++);                    indegree[j]++;                    outdegree[i]++;                }            }        }        int cnt = topo ();        if (cnt != n)            printf ("Yes\n");        else            printf ("No\n");    }    return 0;}
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