UVA 1267-network (Greedy dfs)

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Test instructions: At first there is only one node on the server, in order to let all the leaf node distance from the server is not more than K, we add the server on the non-leaf node, ask the least how many servers to add.

Idea: Greed. The first server node as the root node, the downward expansion, record the parent-child relationship, the depth of the leaf node to sort, starting from the deepest node to find the K-Distance parent node, install the server, and a DFS, will all the distance it does not exceed the node mark of K.

See the code for details:

#include <cstdio> #include <cstring> #include <algorithm> #include <iostream> #include < string> #include <vector> #include <stack> #include <bitset> #include <cstdlib> #include < cmath> #include <set> #include <list> #include <deque> #include <map> #include <queue># Define MAX (a) > (b)? ( A):(B) #define MIN (a) < (b) ( A):(B)) using namespace Std;typedef long long ll;typedef long double ld;const ld EPS = 1e-9, PI = 3.14159265358979323846264 33832795;const int mod = 1000000000 + 7;const int INF = int (1e9); Const LL INF64 = LL (1e18); const int MAXN = + + 10;int    T,n,m,s,k,root,p[maxn];bool vis[maxn];struct Node {int u, D;    Node (int u=0, int d=0): U (u), D (d) {} BOOL operator < (const node& RHS) Const {return d < RHS.D;    }};vector<int> g[maxn];vector<node> d;void Pre (int u, int fa, int cur) {int cnt = g[u].size ();    P[u] = FA; if (cnt = = 1) {D.push_back (Node (u, cur)); return ;        } for (int i=0;i<cnt;i++) {int v = g[u][i];        if (v! = FA) {Pre (V, U, cur+1);    }}}void dfs (int u, int fa, int cur) {if (cur > k) return;    int len = G[u].size ();    Vis[u] = true;        for (int i=0;i<len;i++) {int v = g[u][i];        if (v! = FA) {dfs (V, u, cur+1);    }}}int U, v;int Main () {scanf ("%d", &t);        while (t--) {scanf ("%d%d%d", &n,&s,&k);        for (int i=1;i<=n;i++) g[i].clear ();        D.clear ();            for (int i=1;i<n;i++) {scanf ("%d%d", &u,&v);            G[u].push_back (v);        G[v].push_back (U);        } pre (S, s, 0);        Sort (D.begin (), D.end ());        Memset (Vis, false, sizeof (VIS));        DFS (s, s, 0);        int len = D.size ();        int ans = 0;            for (int i=len-1;i>=0;i--) {node u = d[i];            if (vis[u.u]) continue;            int v = u.u;           for (int j=0;j<k;j++) v = p[v]; DFS (V, v, 0);        ++ans;    } printf ("%d\n", ans); } return 0;}

UVA 1267-network (Greedy dfs)