UVALive-3887 Slim Span (Kruskal)

The main idea: to define the difference between the maximum and the minimum edges of the graph spanning tree is to slim, to find the slender degree of the smallest tree.

Title Analysis: First, all the edges are ordered from small to large, in the continuous interval [l,r] in the edge if it can form a spanning tree, then this tree must have the smallest degree of thinness. Enumerate all of these intervals.

The code is as follows:

# include<iostream># include<cstdio># include<set># include<queue># include<cstring># Include<algorithm>using namespace std;# define REP (i,s,n) for (int i=s;i<n;++i) # define CL (A, B) memset (A, B,    sizeof (a)) # define CLL (A,b,n) Fill (a,a+n,b) const int N=105;CONST int inf=1<<30;struct edge{int u,v,w;    BOOL operator < (const Edge &a) Const {return w<a.w; }};    Edge e[5005];int fa[n],n,m;int Findfa (int u) {if (fa[u]!=u) return Fa[u]=findfa (Fa[u]); return u;}    BOOL Judge () {int cnt=0;    REP (i,1,n+1) if (fa[i]==i) ++cnt; return cnt==1;}    int main () {//freopen ("UVALive-3887 Slim Span.txt", "R", stdin); while (scanf ("%d%d", &n,&m) && (n+m)) {REP (i,0,m) scanf ("%d%d%d", &e[i].u,&e[i].v,&e[i].        W);        Sort (e,e+m);        int ans=inf;            Rep (L,0,m) {rep (i,1,n+1) fa[i]=i;                REP (r,l,m) {int u=e[r].u,v=e[r].v;      int A=findfa (u);          int B=findfa (v);                if (a!=b) fa[a]=b;                    if (judge ()) {ans=min (ANS,E[R].W-E[L].W);                Break        }}} if (Ans==inf) printf (" -1\n");    else printf ("%d\n", ans); } return 0;}

　　

UVALive-3887 Slim Span (Kruskal)