河南第八届省赛（引水工程）（Prim求最小生成树）

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题目地址：点击打开链接

思路：建一个虚拟点，和所有的水库相连权值为自建水库的花费，跑一遍最小生成树就行，蓝桥杯题库的原题

AC代码：

#include <iostream>#include <cstdio>#include <cstdlib>#include <algorithm>#include <queue>#include <stack>#include <map>#include <cstring>#include <climits>#include <cmath>#include <cctype>using namespace std;const int zui = 1000000000;int map1[310][310];int cost[310];int visit[310];int lowdist[310];int n;void Prim(){    memset(visit,0,sizeof(visit));    int i,j,k;    for(i=1; i<=n; i++)    {        lowdist[i] = map1[0][i];    }    visit[0] = 1;    int sum = 0;    for(i=1; i<=n; i++)//要并入n个点所以要循环n次    {        int min2 = zui;        for(j=1; j<=n; j++)        {            if(!visit[j] && lowdist[j] < min2)            {                min2 = lowdist[j];                k = j;            }        }        visit[k] = 1;        sum += lowdist[k];        for(j=1; j<=n; j++)        {            if(!visit[j] && map1[k][j] < lowdist[j])            {                lowdist[j] = map1[k][j];            }        }    }    printf("%d\n",sum);}int main(){    int k;    int i,j;    scanf("%d",&k);    while(k--)    {        scanf("%d",&n);        int cost;        for(i=0; i<=n; i++)        {            for(j=0; j<=n; j++)            {                map1[i][j] = zui;            }        }        for(i=1; i<=n; i++)        {            scanf("%d",&cost);            map1[0][i] = map1[i][0] = cost;            //map1[0][i] = cost;        }        for(i=1; i<=n; i++)        {            for(j=1; j<=n; j++)            {                scanf("%d",&map1[i][j]);            }        }        Prim();    }    return 0;}

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