kuangbin_MST A (POJ 1251)

模板题 Kruskal直接过 调试时候居然在sort(edge + 1, edge + 1 + m)上浪费好多时间...

不过本着ACMer的心态自然要测试一下两种方法分别的速度

Kruskal : Memory 392 Time 16

Prim: Memory 576 Time 16

...........哦居然一样啊

 

Prim

#include <cstdio>
#include <cstring>
#include <queue>
#include <vector>
#include <algorithm>
#define INF 0x3F3F3F3F
using namespace std;

typedef pair<int, int> pii;
struct cmp{
    bool operator() (const pii a, const pii b){
        return a.first > b.first;
    }
};

int size, head[30], point[200], nxt[200], val[200];
int n, dist[30];

void init()
{
    size = 0;
    memset(head, -1 ,sizeof head);
}

void add(int from, int to, int value)
{
    val[size] = value;
    point[size] = to;
    nxt[size] = head[from];
    head[from] = size++;
}

int prim(int s)
{
    int ans = 0;
    bool vis[30];
    memset(dist, 0x3f, sizeof dist);
    memset(vis, false, sizeof vis);
    
    priority_queue<pii, vector<pii>, cmp> q;
    for(int i = head[s]; ~i; i = nxt[i]){
        dist[point[i]] = val[i];
        q.push(make_pair(val[i], point[i]));
    }
    dist[s] = 0;
    vis[s] = true;
    while(!q.empty()){
        pii u = q.top();
        q.pop();
        if(vis[u.second]) continue;
        vis[u.second] = true; 
        ans += u.first;
        for(int i = head[u.second]; ~i; i = nxt[i]){
            int j = point[i];
            //printf("check edge[%d][%d] vis = %d value = %d\n", u.second, j, vis[j], val[i]);
            if(!vis[j] && dist[j] > val[i]){
                //printf("add edge[%d][%d]\n", u.second, j);
                dist[j] = val[i];
                q.push(make_pair(dist[j], j));
            }
        }
    }
    return ans;
}

int main()
{
    while(scanf("%d", &n), n){
        init();
        for(int i = 1; i < n; i++){
            int k;
            scanf("%*s%d", &k);
            while(k--){
                char to[2];
                int value;
                scanf("%s%d", to, &value);
                add(i, to[0]-'A'+1, value);
                add(to[0]-'A'+1, i, value);
            }
        }
        printf("%d\n", prim(1));
    }            
    return 0;
}

Kruskal

#include <cstdio>
#include <cstring>
#include <queue>
#include <vector>
#include <algorithm>
#define INF 0x3F3F3F3F
using namespace std;

int n, m;
int parent[100], rank[100];
struct Edge{int u, v, w;}edge[100];

bool cmp(Edge a, Edge b)
{
    return a.w < b.w;
}

inline int FindSet(int x)
{
    while(x != parent[x]) x = parent[x];
    return x;
}

void UnionSet(int l, int r)
{
    int x = FindSet(l);
    int y = FindSet(r);
    if(rank[x] > rank[y]){
        rank[x] += rank[y];
        parent[y] = x;
    }
    else{
        rank[y] += rank[x];
        parent[x] = y;
    }
}

int kruskal()
{
    for(int i = 1; i <= n; i++){
        parent[i] = i;
        rank[i] = 1;
    }
    int ans = 0;
    sort(edge+1, edge+m+1, cmp);
    for(int i = 1, num = 0; num < n-1 && i <= m; i++){
        int x = FindSet(edge[i].u);
        int y = FindSet(edge[i].v);
        if(x != y){
            num++;
            UnionSet(x, y);
            ans += edge[i].w;
        }
    }
    return ans;
}

int main()
{
    while(scanf("%d", &n), n){
        m = 0;
        for(int i = 1; i < n; i++){
            int k;
            scanf("%*s%d", &k);
            while(k--){
                m++;
                edge[m].u = i;
                char v[2];
                scanf("%s%d", v, &edge[m].w);
                edge[m].v = v[0] - 'A' + 1;
                //printf("Edge %d : u = %d v = %d w = %d\n", m, edge[m].u, edge[m].v, edge[m].w);
            }
        }
        printf("%d\n", kruskal());
    }
    return 0;
}