标签:style blog http io color ar os sp for
题意:在一个有向图上,至少放多少个机器人可以遍历整个图(每个顶点可以重复遍历)?
思路:最小路径覆盖的变形,因为点可以重复遍历,所以要用floyd重新建图,然后用最小路径覆盖去做。
代码:
#include <iostream> #include <cstdio> #include <cstring> #include <vector> #include <algorithm> using namespace std; const int MAXN = 1005; int g[MAXN][MAXN]; int linker[MAXN]; bool used[MAXN]; int n, m; bool dfs(int u) { for (int v = 1; v <= n; v++) { if (g[u][v] && !used[v]) { used[v] = true; if (linker[v] == -1 || dfs(linker[v])) { linker[v] = u; return true; } } } return false; } int hungary() { int res = 0; memset(linker, -1, sizeof(linker)); for (int u = 1; u <= n; u++) { memset(used, false, sizeof(used)); if (dfs(u)) res++; } return res; } int main() { while (scanf("%d%d", &n, &m) && n) { memset(g, 0, sizeof(g)); int u, v; for (int i = 0; i < m; i++) { scanf("%d%d", &u, &v); g[u][v] = 1; } for (int k = 1; k <= n; k++) { for (int i = 1; i <= n; i++) { for (int j = 1; j <= n; j++) { g[i][j] |= (g[i][k]&g[k][j]); } } } printf("%d\n", n - hungary()); } return 0; }
POJ2594-Treasure Exploration(最小路径覆盖变形)
标签:style blog http io color ar os sp for
原文地址:http://blog.csdn.net/u011345461/article/details/40923071