杭电2682--Tree（Prim）

1 for(int i = 1; i <= n; i++)  for(int j  = i; j  <= n; j++)  map[i][j]=map[j][i]=(i==j?0:INF)  
2 
3 和普通写法区别。

#include <cmath>
#include <cstdio>
#include <cstring>
#include <iostream>
#define M 601 
#define N 1000001
using namespace std;
const int INF = 0x3f3f3f3f;
int sieve[N*2], dis[M], vis[M], Rode[M], map[M][M];
int n;
int Min(int a, int b)
{
    if(a < b)
        return a;
    else
        return b;
}
void Is_Prime()
{
    memset(sieve, 0, sizeof(sieve));
    sieve[0] = sieve[1] = 1;
    for(int i = 2; i < N*2; i++)
    {
        if(!sieve[i])
            for(int j = 2*i; j < N*2; j += i)
                sieve[j] = 1;
    }
}
void Prime()
{
    int sum = 0;
    memset(vis, 0, sizeof(vis));
    for(int i = 1; i <= n; i++)
        dis[i] = map[1][i];
    vis[1] = 1;
    for(int i = 1; i < n; i++)
    {
        int temp = 1, min = INF;
        for(int j = 1; j <= n; j++)
        {
            if(!vis[j] && dis[j] < min)
            {
                temp = j;
                min = dis[j];    
            }    
        } 
        if(min == INF)
        {
            printf("-1\n");
            return;
        }
        vis[temp] = 1;
        sum += min;
        for(int j = 1; j <= n; j++)
            if(!vis[j] && dis[j] > map[temp][j])
                dis[j] = map[temp][j];
    }
    printf("%d\n", sum);
}
int main()
{
    int T;
    scanf("%d", &T);
    Is_Prime();
    while(T--)
    {
        scanf("%d", &n);
        for(int i = 1; i <= n; i++)
            scanf("%d", &Rode[i]);
        for(int i = 1; i <= n; i++)
            for(int j = 1; j <= n; j++)
                map[i][j] = (i==j?0:INF);
        for(int i = 1; i <= n; i++)
            for(int j = 1; j <= i; j++)
                if(!sieve[Rode[i]] || !sieve[Rode[j]] || !sieve[Rode[i] + Rode[j]])
                    map[i][j] = map[j][i] = Min(Min(Rode[i], Rode[j]), abs(Rode[i]-Rode[j]));
        Prime();
    }
    return 0;    
}