Ural 1416 confidential subgeneration tree

/*

Question:

For a very bare sub-tree question, the Minimum Spanning Tree value must be given first. If there is an output that is not connected-1,

Then we need to output the next small Spanning Tree value.

Analysis:

Select prim or Kruskal.AlgorithmI use prim to do this. For details, seeCodeNote

 

*/

# Include <iostream>

# Include <cstring>

# Include <cstdio>

Using namespace STD;

# Define x 503

# Define INF 10000000

Int path [x] [X], map [x] [X], DIS [X], pre [X], n, m;

Bool use [X], visit [x] [x];

Int prim ()

{

Memset (PRE, 0, sizeof (pre); // frontend Vertex

Memset (visit, false, sizeof (visit); // indicates whether the edge is in the minimal spanning tree.

Memset (use, false, sizeof (use); // indicates whether the edge is in the Minimum Spanning Tree.

Memset (path, 0, sizeof (PATH); // edge that marks the maximum length between the two vertices

For (INT I = 1; I <= N; I ++)

Dis [I] = inf;

Dis [1] = 0;

Int K, Min, ANS = 0;

For (INT I = 0; I <n; I ++)

{

Min = inf;

For (Int J = 1; j <= N; j ++)

If (! Use [J] & dis [J] <min)

Min = dis [k = J];

If (min = inf) // if there is no connection path, exit directly.

Return INF;

 

Int P = pre [k];

Visit [p] [k] = visit [k] [p] = true; // indicates that the edge is in the Spanning Tree.

Path [p] [k] = min; // represents the minimum length of the edge in the Spanning Tree.

For (Int J = 1; j <= N; j ++)

If (use [J]) // update the distance from all the points in the Minimum Spanning Tree to K. path [J] [k]

Path [J] [k] = path [J] [p]> path [p] [k]? Path [J] [p]: path [p] [k];

Ans + = min;

Use [k] = true;

For (Int J = 1; j <= N; j ++)

If (! Use [J] & dis [J]> map [k] [J])

Dis [J] = map [k] [J], pre [J] = K; // if K can update dis [J], K indicates that K is the PRE of J.

}

Return ans;

}

Int main ()

{

Freopen ("sum. In", "r", stdin );

Freopen ("sum. Out", "W", stdout );

Int x, y, z;

While (CIN> N> m)

{

For (INT I = 1; I <= N; I ++)

For (Int J = 1; j <= N; j ++)

Map [I] [J] = inf;

While (M --)

{

Scanf ("% d", & X, & Y, & Z );

Map [x] [Y] = map [y] [x] = z;

}

Int ans = prim (); // obtain the minimum spanning tree.

If (ANS = inf)

{

Cout <"cost:" <-1 <Endl;

Cout <"cost:" <-1 <Endl;

}

Else

{

Cout <"cost:" <ans <Endl;

Int ans2 = inf;

For (INT I = 1; I <= N; I ++)

For (Int J = 1; j <= N; j ++)

If (! Visit [I] [J] & map [I] [J] <inf)

{// Enumeration edge. If the edge is not in the Minimum Spanning Tree and is connected, replace it with an edge in the Minimum Spanning Tree.

Int temp = ans + map [I] [J]-path [I] [J];

If (temp <ans2)

Ans2 = temp;

}

If (ans2 = inf)

Cout <"cost:" <-1 <Endl;

Else

Cout <"cost:" <ans2 <Endl;

}

}

Return 0;

}