POJ 1679 the Unique MST (sub-niche into a tree)

Test instructions: Determines whether the minimum spanning tree is unique.

Idea: Finding the sub-niche into a tree, if it is equal to the minimum spanning tree, is not unique.

PS Blog

#include <iostream> #include <stdio.h> #include <string.h> using namespace std;
/* For minimum spanning tree, use array max[i][j] to represent the maximum weights in MST in the I-J path, immediately enumerate all edges that are not in MST, replace the edge with the maximum weight, update the answer point number starting from 0 */const int maxn=110;
const INT inf=0x3f3f3f3f;//1061109567 bool VIS[MAXN];
int LOWC[MAXN];
int PRE[MAXN];
int Max[maxn][maxn];//max[i][j] represents the maximum edge right of the path from I to J in the smallest spanning tree bool USED[MAXN][MAXN];
int COST[MAXN][MAXN];

int ans;
    int prim (int cost[][maxn],int n) {int ans=0;
    memset (vis,false,sizeof (VIS));
    memset (max,0,sizeof (Max));
    memset (used,false,sizeof (used));
    Vis[0]=true;
    Pre[0]=-1;
        for (int i=1;i<n;i++) {lowc[i]=cost[0][i];
    pre[i]=0;
    } lowc[0]=0;
        for (int i=1;i<n;i++) {int minc=inf;
        int p=-1;
                for (int j=0;j<n;j++) if (!vis[j]&&minc>lowc[j]) {minc=lowc[j];
            P=j;
        } if (Minc==inf) return-1;
        Ans+=minc;
        Vis[p]=true; USED[P][PRE[P]]=USED[PRE[P]][P]=true;
            for (int j=0;j<n;j++) {if (Vis[j]) Max[j][p]=max[p][j]=max (max[j][pre[p]],lowc[p]);
                if (!vis[j]&&lowc[j]>cost[p][j]) {lowc[j]=cost[p][j];
            Pre[j]=p;
}}} return ans;
    } int smst (int cost[][maxn],int n) {int min=inf;
                for (int i=0;i<n;i++) for (int j=i+1;j<n;j++) if (Cost[i][j]!=inf&&!used[i][j]) {
            Min=min (Min,ans+cost[i][j]-max[i][j]);
} if (Min==inf) return-1;//does not exist return Min;
    } int main () {int t,i,j;
    int n,m;
    int u,v,w;
    scanf ("%d", &t);
        while (t--) {scanf ("%d%d", &n,&m);
                for (i=0;i<n;i++) for (j=0;j<n;j++) {if (i==j) cost[i][j]=0;
            else Cost[i][j]=inf;
            } while (m--) {scanf ("%d%d%d", &u,&v,&w);
            u--;v--;
        Cost[u][v]=cost[v][u]=w; } ans=Prim (cost,n);
        if (ans==-1) printf ("Not unique!\n");
        else if (Ans==smst (cost,n)) printf ("Not unique!\n");
    else printf ("%d\n", ans);
} return 0; }