poj 1258 : Agri-Net (prim)

解法一：

#include<iostream>
using namespace std;
int map[102][102];
int m=0xfffffff;
void prim(int n)
{
int lowcost[102],s[102]={0},i,j,min,k,ans=0;
for(i=1;i<=n;i++)
lowcost[i]=map[1][i];
s[1]=1;

for(i=1;i<n;i++)
{
min=m;
j=1;
for(k=2;k<=n;k++)
if((lowcost[k]<min) && !s[k])
{
min=lowcost[k];
j=k;
}
ans+=min;
s[j]=1;
for(k=2;k<=n;k++)
if((map[j][k]<lowcost[k]) && !s[k])
lowcost[k]=map[j][k];
}

cout<<ans<<endl;
}

int main()
{
int n,i,j;
while(scanf("%d",&n)!=EOF)
{
for(i=1;i<=n;i++)
for(j=1;j<=n;j++)
cin>>map[i][j];
prim(n);
}
return 0;
}

解法二：

#include<iostream>
using namespace std;
const int Max = 102;
const int inf = 0xfffffff;

 

int n, ans;
int map[Max][Max], dis[Max];   //  dis[i]表示顶点i与生成树之间的最短距离。

 

int min(int a, int b){
    return a < b ? a : b;
}

 

void prim()

{   
    int i, j, now, min_node, min_edge;
    for(i = 1; i <= n; i ++)
        dis[i] = inf;
    now = 1;
    ans = 0;
    for(i = 1; i < n; i ++){
        dis[now] = -1;    //   将dis[]的值赋-1，表示已经加入生成树中。
        min_edge = inf;
        for(j = 1; j <= n; j ++)    //   更新每个顶点所对应的dis[]值。
            if(now != j && dis[j] >= 0){
                dis[j] = min(dis[j], map[now][j]);
                if(dis[j] < min_edge){
                    min_edge = dis[j];
                    min_node = j;
                }
            }
        now = min_node;
        ans += min_edge;
    }
}

 

int main(){
    int i, j;
    while(scanf("%d", &n) != EOF){
        for(i = 1; i <= n; i ++)
            for(j = 1; j <= n; j ++)
                scanf("%d", &map[i][j]);
        prim();
        printf("%d\n", ans);
    }  
    return 0;
}