World islands -- prim

Link address:

Http://acm.hdu.edu.cn/showproblem.php? PID = 1, 3405

 

The question is to find an MST, but not n vertices. It is n-1 vertices, And the other vertices are isolated.

 

I isolated n vertices and each vertex, figured out the shortest path of all MST, and finally found the minimum value.

 

Code# Include <cstdlib> <br/> # include <cmath> <br/> # include <algorithm> <br/> # include <vector> <br/> # include <iostream> <br/> # include <cstdio> <br/> using namespace STD; <br/> # include <cstring> <br/> const int INF = 20000000; <br/> typedef struct <br/>{< br/> int X, Y; <br/>} node; <br/> node T [51]; <br/> int map [51] [51]; <br/> int shst [51]; <br/> bool used [51]; <br/> int N; <br/> inline int dist (int I, Int J) <br/> {<Br/> int tt; <br/> TT = (T [I]. x-T [J]. x) * (T [I]. x-T [J]. x) + (T [I]. y-T [J]. y) * (T [I]. y-T [J]. y); <br/> return tt; <br/>}< br/> void input () <br/>{< br/> for (INT I = 1; I <= N; I ++) <br/> {<br/> scanf ("% d", & T [I]. x, & T [I]. y); <br/>}< br/> for (INT I = 1; I <= N; I ++) <br/> for (Int J = 1; j <= I; j ++) <br/>{< br/> if (I! = J) <br/>{< br/> map [J] [I] = map [I] [J] = dist (I, j ); <br/>}< br/> else <br/> map [I] [J] = 0; <br/>}</P> <p> double solve (int u) /// U is an isolated island <br/>{< br/> int start; <br/> int I, J, K, KK; <br/> for (I = 1; I <= N; I ++) <br/> used [I] = false; <br/> used [u] = true; <br/> If (u! = 1) Start = 1; <br/> else start = 2; <br/> for (I = 1; I <= N; I ++) <br/> shst [I] = map [start] [I]; <br/> used [start] = true; <br/> shst [start] = shst [u] = 0; <br/> //// there are already two vertices: "accessed ", also find N-2 Points <br/> for (I = 1; I <= n-2; I ++) <br/> {<br/> KK = inf; <br/> for (j = 1; j <= N; j ++) <br/>{< br/> If (! Used [J] & shst [J] <KK) <br/> KK = shst [J], K = J; <br/>}< br/> used [k] = true; <br/> for (j = 1; j <= N; j ++) <br/>{< br/> If (! Used [J] & shst [J]> map [k] [J]) <br/> shst [J] = map [k] [J]; <br/>}</P> <p> double Total = 0; <br/> for (I = 1; I <= N; I ++) <br/>{< br/> total + = SQRT (double) shst [I]); <br/>}< br/> return total; <br/>}< br/> int main () <br/> {<br/> // freopen ("1.in"," r ", stdin ); <br/> int t; <br/> double ans; <br/> CIN> T; <br/> while (t --) <br/>{< br/> scanf ("% d", & N); <br/> input (); <br/> double gyc = 20000000; <br/> for (INT I = 1; I <= N; I ++) <br/> {<br/> ans = solve (I ); <br/> If (gyc> ans) <br/> gyc = ans; <br/>}< br/> printf ("%. 2lf/N ", gyc); <br/>}< br/> return 1; <br/>}< br/>:

 

Prim is used.