UVA 10397 Connect the Campus Kruskal | | Prim

The problem with UVA is always difficult ... Will always beat around the bush, this topic gives some buildings have been built between the fiber optic cable, let the minimum spanning tree, I still prefer to use Kruskal algorithm, but this topic affirmation with prim relatively fast, prim complexity is N^2,kruskal complexity eloge.

When using Kruskal, we need to pre-use and check the set to deal with the cable that has been built, so that they belong to the same ancestor;

Use the prim algorithm when you need to set their side to 0, so that the sum of the time will not be added.

Code: (Kruskal)

#include <iostream> #include <cstdio> #include <cstdlib> #include <cstring> #include <cmath > #include <vector> #include <set> #include <string> #include <algorithm> #define MAX 0x7fffffffusing namespace Std;struct node{int i,j;double len; Gra[640000];int p[800],n;int cmp (const void *a,const void *b) {return (node *) a)->len-((node *) b)->len >0? 1:- 1;} int find (int x) {if (x = = P[x]) return X;elsereturn p[x] = find (P[x]);} int a[800],b[800];d ouble dist (int a,int b,int c,int d) {return sqrt ((a-c) * (a-c) + (b-d) * (b-d));} void Kruskal () {int i; Double sum = 0;for (i=1; i<=n* (n-1)/2; i++) {int x = find (gra[i].i); int y = find (GRA[I].J); if (x! = y) {sum + = Gra[i].len;p [x] = y; }}//cout << sum << endl;printf ("%.2lf\n", sum);} int main () {int i,j,m,x,y;while (cin >> N) {int k = 1;for (i=1; i<=n; i++) cin >> A[i] >> b[i];for (i=1; i& lt;=n-1; i++) for (j=i+1; j<=n; J + +) {gra[k].i = I;GRA[K].J = J;gra[k].len = Dist (a[i],b[i],a[j],b[j]); k++;} CIN >> M;for (i=1; i<=n; i++) P[i] = I;for (i=1; i<=m; i++) {cin >> x >> y;int xx = find (x); int yy = f IND (y); if (xx! = yy) p[xx] = yy;} Qsort (Gra+1,k-1,sizeof (gra[0]), CMP); Kruskal ();} return 0;}

Code (PRIM):

#include <iostream> #include <cstdio> #include <cstdlib> #include <cstring> #include <cmath > #include <vector> #include <set> #include <string> #include <algorithm> #define MAX 0x7fffffffusing namespace Std;double gra[800][800]; int M,n;int visit[800];d ouble d[800];int xx;d ouble dist (int a,int b,int c,int d) {return sqrt ((a-c) * (a-c) + (b-d) * (b-d));} V  OID Prim () {int i,j,now;double sum = 0;double min;xx = 1;d[xx] = 0; visit[xx] = 1; now = Xx;for (i=2; i<=n; i++) {for (j=1; j<=n; J + +) if (!visit[j] && d[j] > Gra[now][j]) d[j] = Gra[now][j]; min = Max;for (j=1; j<=n; j + +) if (!visit[j] && min > d[j]) min = D[now = J];visit[now] = 1;//printf ("now =%d\n ", now);//cout << min << endl;sum + = min;} printf ("%.2lf\n", sum);}  int main () {int i,j;int a[800],b[800];while (cin >> N) {for (i=1; i<=n; i++) cin >> A[i] >> b[i];for (i=1; i<=n-1; i++) for (j=i+1; j<=n; j + +) Gra[i][j] = gra[j][i] = dist (a[i],b[i],a[j],b[j]); CIN >> M;memset (visit,0,sizeof (visit)); for (i=1; i<=n; i++) d[i] = Max;int x,y;for (i=1; i<=m; i++) {cin >> X & gt;> Y;gra[x][y] = gra[y][x] = 0;} Prim ();} return 0;}

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UVA 10397 Connect the Campus Kruskal | | Prim