POJ 1861 Networks

并查集 + 贪心 + 快速排序 求最小生成树

#include <iostream>
#include <memory>
#define MAX_HUB_NUM 1005
#define MAX_EDGE_NUM 15005
using namespace std;

int edge[3][MAX_EDGE_NUM + 1];
int head[MAX_HUB_NUM + 1];
int resEdge[MAX_EDGE_NUM + 1];
int hub_num;
int edge_num;

void swap1(int pos1, int pos2)
{
int temp0 = edge[0][pos2];
int temp1 = edge[1][pos2];
int temp2 = edge[2][pos2];

edge[0][pos2] = edge[0][pos1];
edge[1][pos2] = edge[1][pos1];
edge[2][pos2] = edge[2][pos1];

edge[0][pos1] = temp0;
edge[1][pos1] = temp1;
edge[2][pos1] = temp2;
}

void swap2(int pos1, int pos2)
{
int temp = resEdge[pos2];
resEdge[pos2] = resEdge[pos1];
resEdge[pos1] = temp;
}

int comp1(int pos1, int pos2)
{
if(edge[0][pos1] < edge[0][pos2])
return -1;
else if(edge[0][pos1] == edge[0][pos2])
return 0;
else
return 1;
}

int comp2(int p1, int p2)
{
int pos1 = resEdge[p1];
int pos2 = resEdge[p2];
if(edge[1][pos1] < edge[1][pos2])
return -1;
else if(edge[1][pos1] == edge[1][pos2])
{
if(edge[2][pos1]  < edge[2][pos2])
return -1;
else if(edge[2][pos1]  == edge[2][pos2])
return 0;
else
return 1;
}
else
return 1;
}
void fast_sort(int start, int end, int (*comp)(int pos1, int pos2), void (*swap)(int pos1, int pos2))
{
if(start < end)
{
int pos_s = start;
int pos_e = end + 1;
while(true)
{
while(++pos_s < end && comp(start, pos_s) == 1);
while(--pos_e > start && comp(start, pos_e) == -1);
if(pos_s < pos_e)
swap(pos_s, pos_e);
else
break;
}
swap(start, pos_e);
fast_sort(start, pos_e - 1, comp, swap);
fast_sort(pos_e + 1, end, comp, swap);
}
}

void init_input()
{
memset(edge, 0, sizeof(edge));
memset(head, 0, sizeof(head));
memset(resEdge, 0, sizeof(resEdge));
cin>>hub_num>>edge_num;
for(int i = 1; i <= edge_num; i++)
{
cin>>edge[1][i]>>edge[2][i]>>edge[0][i];
if(i <= hub_num)
head[i] = i;
}
fast_sort(1, edge_num, &comp1, &swap1);
}

int find(int x)
{
if(head[x] == x)
return x;
else
return find(head[x]);
}

void join(int x, int y)
{
int head1 = find(x);
int head2 = find(y);
head[head1] = head2;
}

int main()
{
int i = 1;
int total = 0;
int maxv = 0;
int pos1, pos2, curVal;
init_input();
while(i <= edge_num && total < (hub_num - 1))
{
curVal = edge[0][i];
pos1 = find(edge[1][i]);
pos2 = find(edge[2][i]);
if(pos1 != pos2)
{
if(curVal > maxv)
maxv = curVal;
join(pos1, pos2);
total ++;
resEdge[total] = i;
}
i++;
}
cout<<maxv<<endl;
cout<<total<<endl;

fast_sort(1, total, &comp2, &swap2);

for(i = 1; i <= total; i++)
{
cout<<edge[1][resEdge[i]]<<" "<<edge[2][resEdge[i]]<<endl;
}

return 0;
}