hdu 1811 Rank of Tetris（拓扑排序+并查集）

不熟悉的点：

1.并查集的按秩压缩

2.vector建图

3.bfs拓扑排序

#include "cstdio"
#include "iostream"
#include "cstring"
#include "vector"
#include "queue"
using namespace std;
const int N = 10005;
int n, m, t;
int fa[N];
int X[2 * N], Y[2 * N];
int son[N];
char O[2 * N];
vector<int>G[N];

void init(int n)
{
    for (int i = 0; i <= n; ++i)
        fa[i] = -1;
    for (int i = 0; i <= n; ++i)
        G[i].clear();
    memset(son, 0, sizeof(son));
}
int find(int x)
{
    if (fa[x] < 0) return x;
    return fa[x] = find(fa[x]);
}

bool merg(int a, int b)
{
    int x = find(a);
    int y = find(b);
    if (x == y) return false;
    else if (x < y){
        fa[x] += fa[y];
        fa[y] = x;
    }
    else {
        fa[y] += fa[x];
        fa[x] = y;
    }
    return true;
}

int main()
{
    while (cin >> n >> m) {
        init(n);
        int num = n;
        for (int i = 0; i < m; ++i) {
            cin >> X[i] >> O[i] >> Y[i];
            if (O[i] == '=') {
                if (merg(X[i], Y[i]))
                    num--;
            }
        }
        for (int i = 0; i < m; ++i) if (O[i] != '=') {
            int x = find(X[i]);
            int y = find(Y[i]);
            if (O[i] == '>') {
                G[x].push_back(y);
                son[y]++;
            }
            else {
                G[y].push_back(x);
                son[x]++;
            }
        }
        queue<int> q;
        for (int i = 0; i < n; ++i)
            if (son[i] == 0 && i == find(i))
                q.push(i);
        int sin = 0;
        while (!q.empty()) {
            if (q.size() > 1) sin = 1;
            int t = q.front();
            q.pop();
            --num;
            for (int v = 0; v < G[t].size(); ++v) {
                if (--son[G[t][v]] == 0)
                    q.push(G[t][v]);
            }
        }
        if (num > 0) cout << "CONFLICT" << endl;
        else if (sin) cout << "UNCERTAIN" << endl;
        else cout << "OK" << endl;
    }
    return 0;
}