poj2485 kruskal与prim

#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;

#define debug
#if defined debug
#define CDBG(format,...) printf("File: "__FILE__", Line: %05d: "format"\n", __LINE__, ##__VA_ARGS__)  
int open_file(){
    FILE *fp ;
    if((fp = freopen("input3.txt","r",stdin)) == NULL){
        CDBG("error in freopen");
        return -1;
    }
    CDBG("success in freopen");
    return 0;
}
#else
#define CDBG(format,...) do{}while(0)
#endif

#define N 510
int n,k,pre[N];
struct point
{
    int x;
    int y;
    int len;
}p[N*N];
/*int cmp(const void * x,const void * y)
{
    return ((point*)x)->len>((point*)y)->len?1:-1;
}*/

void swap(point &x,point &y)
{
   point temp;
   temp = x;
   x = y;
   y = temp; // 从指针改成数组就行了
}

int choose_pivot(int i,int j )
{
   return((i+j) /2);
}
//会超时
void quicksort(point list[],int m,int n)
{
   int key,i,j,k;
   if( m < n)
   {
      k = choose_pivot(m,n);
　　　 if(m != k)
      swap(list[m],list[k]);
      key = list[m].len;
      i = m+1;
      j = n;
      while(i <= j)
      {
         while((i <= n) && (list[i].len <= key)) i++;
         while((j >= m) && (list[j].len > key)) j--;
         if( i < j)
                swap(list[i],list[j]);
      }
     // 交换两个元素的位置
　　　 if(m != j)
      swap(list[m],list[j]);
     // 递归地对较小的数据序列进行排序
      quicksort(list,m,j-1);
      quicksort(list,j+1,n);

  }

}


int cmp(point x,point y)
{
    return x.len<y.len;
}
int find(int x)
{
    while(x!=pre[x]) x=pre[x];
    return x;
}
void kruskal()
{
    int i,mix,a,b;
    mix=0;
    //sort(p,p+k,cmp);
    for(i = 0; i < k ;i++)
    CDBG("%d ",p[i].len);
    quicksort(p,0,k-1);  //跟 sort 结果完全不一样
    for(i = 0; i < k ;i++)
    CDBG("%d ",p[i].len);
    for(i=1;i<=n;i++)
        pre[i]=i;
    for(i=0;i<k;i++)
    {
        a=find(p[i].x);
        b=find(p[i].y);
        if(a!=b)
        {
            if(p[i].len>mix)
                mix=p[i].len;
            pre[b]=a;
        }
    }
    cout<<mix<<endl;
}
void input()
{
    scanf("%d",&n);
    k=0;
    for(int i=1;i<=n;i++)
    for(int j=1;j<=n;j++)
        {
            scanf("%d",&p[k].len);
            if(i != j && p[k].len != 0){
                p[k].x=i;
                p[k].y=j;
                k++;  //过滤掉ii 点
            }
        }
}
int main()
{
    int T;
    #ifdef debug
    if(open_file() != 0)
        return -1;
    #endif
    scanf("%d",&T);
    while(T--)
    {
        input();
        kruskal();
    }
    return 0;
}

#include<stdio.h>    
#include<string.h>

#define debug
#if defined debug
#define CDBG(format,...) printf("File:"__FILE__", Line:%05d: "format"\n", __LINE__, ##__VA_ARGS__)  
#else
#define CDBG(format,...) do{}while(0)
#endif

#define N 511   
// n -> [3,500]
#define inf 0x3f3f3f3f
//distance -> [1,65536]

int villages[N][N];
int visited[N];    
int lowcost[N];


int open_file(){
    FILE *fp ;
    if((fp = freopen("input3.txt","r",stdin)) == NULL){
        CDBG("error in freopen");
        return -1;
    }
    CDBG("success in freopen");
    return 0;
}

void reset_visited(int n){
    int i = 1;
    for( i = 1; i<= n; i++){ visited[i] = 0; lowcost[i] = 0;}
}
//下面2个方法都可以
int prim(int start_p,int n){
    int i,j,pos,min = 0,result = 0;
    reset_visited(n);
    //start at point 1
    visited[start_p] = 1; pos = start_p;
    //set low array from point 1 to other point
    for(i = 1; i <= n; i++)
        if(i != pos) {
            lowcost[i] = villages[pos][i];
            CDBG("set lowcost[%d] = %d",i,lowcost[i]);
        }
    //check n-1 times again
    for(i = 1; i < n; i++){ // 使用 while循环代替 for 容易有一些问题
        //find min distance 寻找下一个最短距离
        min = inf;
        for(j = 1; j <= n; j++){
            if(visited[j] == 0 && lowcost[j] < min)
                {
                    min = lowcost[j];pos = j;
                    CDBG("min = %d pos = %d j = %d",min,pos,j);
                }
        }
        CDBG("min = %d pos = %d ",min,pos);
        //add min distance;
        if(result < min)
        result = min;
        
        visited[pos] = 1;
        //update
        for(j = 1; j <= n; j++){
            if(visited[j] == 0 && lowcost[j] > villages[pos][j])
            {
                lowcost[j] = villages[pos][j];
                CDBG("update lowcost[%d] = %d",j ,lowcost[j]);
            }
        }    
    }
    return result;                    
}

int prim(int n)  
{  
    int u = 1;
    int i,j,k,start,min,max;  
    //memset(vis,0,sizeof(vis)); 
    reset_visited(n);    
    for(i=1;i<=n;i++)  
        if(i!=u)  
            lowcost[i]=villages[1][i];  
    visited[1]=true;  
    k=0;  
    min=0;max=0;  
    for(i=1;i<n;i++)        //n-1条边   
   {  
        min=inf;  
        for(j=1;j<=n;j++)  
        if(lowcost[j]<min&&!visited[j])  
        {  
            min=lowcost[j];  
            k=j;  
        }  
        if(min>max)  
        max=min;  
        visited[k]=true;  
        for(j=1;j<=n;j++)  
       if(lowcost[j]>villages[k][j]&&!visited[j])  
        {  
            lowcost[j]=villages[k][j];  
        }  
    }  
    return max;
    //cout<<max<<endl;  
}

void read_villages(int n){
    for(int i = 1; i <= n; i++)
        for(int j = 1; j <= n; j++)
            {
                villages[i][j] = 0;
                scanf("%d",&villages[i][j]);
            }
}
void check_villages(int n){
    for(int i = 1; i <= n; i++){
        for(int j = 1; j <= n; j++)
            printf("%d ",villages[i][j]);  // 应该是这个导致了 Output Limit Exceeded     
    printf("\n");        
    }
}
int main(){    
    int T,n;
#ifdef debug
    if(open_file() != 0)
        return -1;
#endif

    scanf("%d",&T);
    while(T--){
        scanf("%d",&n);
        read_villages(n);
        //check_villages(n);        
        int ans=0;
        ans = prim(2,n); // 可以从任意一点开始
        //ans = prim(n);
        printf("%d\n",ans);
    }

    return 0;
}