poj2075

最小生成树，我是用邻接表+map存储姓名做的，点开1000就够了。

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <map>
using namespace std;

#define inf 0x3f3f3f3f
#define maxn 1005
#define maxl 25

struct Edge
{
    int v, next;
    double w;
}edge[maxn * maxn];

int vis[maxn];
double lowc[maxn];
double len;
int n, m;
int head[maxn];
int ncount;
map <string, int> name;

void addedge(int a, int b, double w)
{
    edge[ncount].v = b;
    edge[ncount].next = head[a];
    edge[ncount].w = w;
    head[a] = ncount++;
}

void input()
{
    scanf("%lf%d", &len, &n);
    for (int i = 0; i < n; i++)
    {
        char ch[maxl];
        scanf("%s", ch);
        string st(ch);
        name[ch] = i;
    }
    scanf("%d", &m);
    for (int i = 0; i < m; i++)
    {
        char ch1[maxl], ch2[maxl];
        double w;
        scanf("%s%s%lf", ch1, ch2, &w);
        string st1(ch1), st2(ch2);
        int a = name[st1];
        int b = name[st2];
        addedge(a, b, w);
        addedge(b, a, w);
    }
}

double prim()
{
    memset(vis, 0, sizeof(vis));
    for (int i = 0; i < n; i++)
        lowc[i] = inf;
    lowc[0] = 0;
    double ret = 0;
    lowc[n] = inf;
    while (true)
    {
        int u = n;
        for (int i = 0; i < n; i++)
            if (lowc[u] > lowc[i] && !vis[i])
                u = i;
        if  (u == n)
            break;
        vis[u] = true;
        ret += lowc[u];
        lowc[u] = 0;
        for (int i = head[u]; ~i; i = edge[i].next)
        {
            int v = edge[i].v;
            lowc[v] = min(lowc[v], edge[i].w);
        }
    }
    return ret;
}

int main()
{
    //freopen("t.txt", "r", stdin);
    memset(head, -1, sizeof(head));
    ncount = 0;
    input();
    double ans = prim();
    if (ans > len)
        printf("Not enough cable\n");
    else
        printf("Need %.1f miles of cable\n", ans);
    return 0;
}