poj2421——Constructing Roads

将已修好的边赋值为0，套用prim()模板，1A.

#include<stdio.h>#include<string.h>#define maxcost 999999999int g[105][105];int n,m;int pre[105],dist[105],vis[105];int prim(int v){int i,j,dis,min,k,ans=0;memset(vis,true,sizeof(vis));for(i=1;i<=n;i++){pre[i]=1;dist[i]=g[v][i];}vis[1]=false;dist[1]=0;for(i=1;i<=n;i++){min=maxcost;k=v;for(j=1;j<=n;j++){if(dist[j]<min&&vis[j]){min=dist[j];k=j;}}if(min!=maxcost){ans+=min;}vis[k]=false;for(j=1;j<=n;j++){if(vis[j]&&dist[j]>g[k][j]&&g[k][j]!=maxcost){dist[j]=g[k][j];pre[j]=k;} }}return ans;}int main(){int i,j,a,b;scanf("%d",&n);for(i=1;i<=n;i++){for(j=1;j<=n;j++)scanf("%d",&g[i][j]);}scanf("%d",&m);while(m--){scanf("%d%d",&a,&b);g[a][b]=0;g[b][a]=0;}printf("%d/n",prim(1));}

kruskal算法：

#include <stdio.h>#include <iostream>#include<string>#include<algorithm>using namespace std;int shortest;typedef struct _node{ int x; int y; int distance; }Node;int root[120];int heavy[120];Node graph[120*120] = {0};int compare(Node a, Node b){ return a.distance<b.distance; }int findset(int i){ if (root[i] != i) root[i] = findset(root[i]); return root[i]; }void makeset(int i){ root[i] = i; heavy[i] = 1; }void unio(int i, int j){ if(i<j)root[j]=i;else root[i]=j;}void kruskal(int i){ int t, k; t = findset(graph[i].x); k = findset(graph[i].y); if (t != k) { shortest = shortest + graph[i].distance; unio(t, k); } }int main(){ int N,i,Q; int index; while(scanf("%d", &N)!=EOF){index = -1; shortest = 0; for (i = 0; i < N; ++i) //input the data into graph struct { for (int j = 0; j < N; ++j) { index++; graph[index].x = i; graph[index].y = j; scanf("%d", &graph[index].distance); } }sort(graph, graph+N*N,compare);//sort the data in the graph for (i = 0; i < N; ++i) makeset(i); scanf("%d",&Q);int x,y;for(i=1;i<=Q;i++){ scanf("%d %d",&x,&y); unio(findset(x-1),findset(y-1));}for (i = 0; i < N*N; ++i) kruskal(i); printf("%d/n",shortest); }return 0; }