uva10304 Ordering-Tasks 拓扑排序

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拓扑排序的邻接表和矩阵实现
利用二维数组稀疏表很浪费空间，利用邻接表更好。
利用邻接表要堤防重复值。
例如：1,3 1,3 二维数组把一个结点赋1，但是邻接表在一个节点下会出现两个值。
设置visited数组之后一般不用担心邻接表重复值影响结果。

题目链接：http://acm.hust.edu.cn/vjudge/problem/viewProblem.action?id=19451

//二维数组实现#include<cstdio>#include<iostream>#include<sstream>#include<cstdlib>#include<cmath>#include<cctype>#include<string>#include<cstring>#include<algorithm>#include<stack>#include<queue>#include<set>#include<map>#include<ctime>#include<vector>#include<fstream>using namespace std;int G[101][101];stack<int>topo;int visited[105];int n,m;bool dfs(int v){    visited[v] = -1;    for(int i = 1; i <= n; ++i)    {        if(G[v][i])        {            if(visited[i] < 0)                return false;            else if(!visited[i] && !dfs(i))                return false;        }    }    visited[v] = 1;    topo.push(v);    return true;}bool topoSort(){    for(int i = 1; i <= n; ++i)    {        if(!visited[i])            if(!dfs(i))                return false;    }    return true;}int main(){    //freopen("F:\\data.txt","r",stdin);    int a,b;    while(scanf("%d%d",&n,&m) != EOF)    {        if(n == 0 && m == 0)            break;        memset(G,0,sizeof(G));        memset(visited,0,sizeof(visited));        for(int i = 0; i < m; ++i)        {            scanf("%d%d",&a,&b);            G[a][b] = 1;        }        topoSort();//利用返回值可以检测是否有回路        printf("%d",topo.top());//利用栈来输出        topo.pop();        for(int i = 1; i < n; ++i)        {            printf(" %d",topo.top());            topo.pop();        }        printf("\n");    }    return 0;}//vector<vector<int> >G实现；#include<cstdio>#include<iostream>#include<sstream>#include<cstdlib>#include<cmath>#include<cctype>#include<string>#include<cstring>#include<algorithm>#include<stack>#include<queue>#include<set>#include<map>#include<ctime>#include<vector>#include<fstream>using namespace std;vector<vector<int> >G;stack<int>topo;int visited[105];bool dfs(int n){    int t;    visited[n] = -1;    int l = G[n].size();    for(int i = 0; i < l; ++i)    {        t = G[n][i];        if(visited[t] == -1)            return false;        else if(!visited[t] && !dfs(t))            return false;    }    visited[n] = 1;    topo.push(n);    return true;}bool topoSort(int n){    for(int i = 1; i <= n; ++i)    {        if(!visited[i])            if(!dfs(i))                return false;    }    return true;}int main(){    //freopen("F:\\data.txt","r",stdin);    int n,m;    int a,b;    while(scanf("%d%d",&n,&m) != EOF)    {        if(n == 0 && m == 0)            break;        G.resize(n+5);        G.clear();        memset(visited,0,sizeof(visited));        for(int i = 0; i < m; ++i)        {            scanf("%d%d",&a,&b);            G[a].push_back(b);        }        topoSort(n);//可以通过返回值判断是否有回路        printf("%d",topo.top());        topo.pop();        for(int i = 1; i < n; ++i)        {            printf(" %d",topo.top());            topo.pop();        }            printf("\n");    }    return 0;}

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