Uva - 10305 - Ordering Tasks

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把小于关系看成有向边，就变成了一个有向图，问题抽象为拓扑排序。

结果比较多，所以跑出来的测试数据和给的结果不一样，不过这个正常，也AC了。

AC代码：

#include <iostream>#include <cstdio>#include <cstdlib>#include <cctype>#include <cstring>#include <string>#include <sstream>#include <vector>#include <set>#include <map>#include <algorithm>#include <stack>#include <queue>#include <bitset> #include <cassert> using namespace std;const int maxn = 1000;int n, m, G[maxn][maxn], c[maxn], topo[maxn], t;bool dfs(int u) {c[u] = -1; // 等于-1表示正在访问for (int v = 0; v < n; v++) {if (G[u][v]) {if (c[v] < 0) { // 存在有向环，失败return false;}else if (!c[v]) {dfs(v);}}}c[u] = 1;topo[--t] = u;return true;}bool toposort(){t = n;memset(c, 0, sizeof(c));for (int u = 0; u < n; u++) {if (!c[u]) {if (!dfs(u)) {return false;}}}return true;}int main(){while (scanf("%d", &n)&& n) {scanf("%d", &m);memset(G, 0, sizeof(G));for (int i = 0; i < m; i++) {int u, v;scanf("%d%d", &u, &v);u--;v--;G[u][v] = 1;}if (toposort()) {for (int i = 0; i < n - 1; i++) {printf("%d ", topo[i] + 1);}printf("%d\n", topo[n - 1] + 1);}else {printf("No\n");}}return 0;}

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