hdu 1863 畅通工程（最小生成树，kruskal）

来源：互联网发布：java如何比较日期大小编辑：程序博客网时间：2024/05/29 07:18

#include <cstdio>#include <algorithm>using namespace std;struct node{    int u,v,w;};node e[5005];int f[101];int n,m;bool cmp(node& a , node& b){    return a.w < b.w;}int getf(int x){    if(x == f[x])        return x;    else    {        f[x] = getf(f[x]);        return f[x];    }}int merges(int x, int y){    int t1,t2;    t1 = getf(x);    t2 = getf(y);    if(t1 != t2)    {        f[t2] = t1;        return 1;    }    return 0;}int main(){    while(scanf("%d %d",&m,&n) && m)    {        for(int i = 1; i <= m; ++i)            scanf("%d %d %d",&e[i].u,&e[i].v,&e[i].w);        sort(e+1,e+m+1,cmp);        for(int i = 1; i <= n; ++i)            f[i] = i;        int sum = 0, counts = 0,flag = 0;        for(int i = 1; i <= m; ++i)        {            if(merges(e[i].u,e[i].v))            {                ++counts;                sum += e[i].w;            }            if(counts == n-1)            {                flag = 1;                break;            }        }        if(flag)            printf("%d\n",sum);        else            printf("?\n");    }    return 0;}

上边的代码15ms，

下边的0ms

#include <iostream>#include <algorithm>using namespace std;int n,m;int f[101],u[5005],v[5005],w[5005],r[5005];bool cmp(const int& i, const int& j){    return w[i] < w[j];}int getf(int x){    return f[x] == x ? x:(f[x] = getf(f[x]));}int main(){    int sum,counts;    while((cin >> m >> n) && m)    {        sum = 0;        counts = 0;        for(int i = 0; i < m; ++i)            cin >> u[i] >> v[i] >> w[i];        for(int i = 0; i < m; ++i) r[i] = i;        for(int i = 0; i <= n; ++i) f[i] = i;        sort(r,r+m,cmp);        for(int i = 0; i < m; ++i)        {            int e = r[i];            int x = getf(u[e]);            int y = getf(v[e]);            if(x != y)            {                ++counts;                sum += w[e];                f[y] = x;            }        }        if(counts == n-1)            cout << sum << endl;        else            cout << "?" << endl;    }    return 0;}

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