hdu 1181

来源：互联网发布：腹肌撕裂者软件编辑：程序博客网时间：2024/06/04 17:58

并查集 + 拓扑排序。

拓扑排序具体怎么用还要学习，这个题里面就是从入度为零开始算起。一次只有一个入度为零，若大于一，则UNCERTAIN 如果执行完毕，还有数字没被计算，那么有环，则CONFLICT；

#include<cstdio>#include<vector>#include<cstring>#include<queue>using namespace std;const int maxn = 10000 + 5;struct node{    int a,b;    char op;} ship[maxn];int pre[maxn];vector<int> u[maxn];int in[maxn];int n, m, sum;void init(){    sum = n;    for(int i = 0; i <= n; i++)        u[i].clear();    for(int i = 0; i <= n; i++)        pre[i] = i;    memset(in, 0, sizeof(in));}int root(int x){    if(x != pre[x])        pre[x] = root(pre[x]);    return pre[x];}int merge_set(int x, int y){    int fx = root(x);    int fy = root(y);    if(fx == fy) return false;    else    {        pre[fx] = fy;        return true;    }}void top_sort(){    int little = false;    queue<int> q;    for(int i = 0; i < n; i++)    {        if(pre[i] == i && !in[i])            q.push(i);    }    while(!q.empty())    {        if(q.size() > 1) little = true;        int t = q.front();        sum--;        q.pop();        for(int i = 0; i < u[t].size(); i++)        {            in[u[t][i]]--;            if(in[u[t][i]] == 0)            {                q.push(u[t][i]);            }        }    }    if(sum > 0) printf("CONFLICT\n");    else if(little) printf("UNCERTAIN\n");    else printf("OK\n");}int main(){    while(scanf("%d%d", &n, &m) == 2)    {        init();        for(int i = 0; i < m; i++)        {            scanf("%d %c %d", &ship[i].a, &ship[i].op, &ship[i].b);            if(ship[i].op == '=')            {                if(merge_set(ship[i].a, ship[i].b))                    sum--;            }        }        for(int i = 0; i < m; i++)            if(ship[i].op != '=')            {                int f = root(ship[i].a), s = root(ship[i].b);                if(ship[i].op == '>')                {                    u[f].push_back(s);                    in[s]++;                }                else                {                    u[s].push_back(f);                    in[f]++;                }            }        top_sort();    }    return 0;}

阅读全文

0 0