# Light OJ 1123 – Trail Maintenance

0

Problem Link : http://www.lightoj.com/volume_showproblem.php?problem=1123

```
/*
+-+ +-+ +-+
|R| |.| |S|
+-+ +-+ +-+
*/

#include <bits/stdc++.h>

#define pii             pair <int,int>
#define sc              scanf
#define pf              printf
#define Pi              2*acos(0.0)
#define ms(a,b)         memset(a, b, sizeof(a))
#define pb(a)           push_back(a)
#define MP              make_pair
#define db              double
#define ll              long long
#define EPS             10E-10
#define ff              first
#define ss              second
#define sqr(x)          (x)*(x)
#define D(x)            cout<<#x " = "<<(x)<<endl
#define VI              vector <int>
#define DBG             pf("Hi\n")
#define MOD             100007
#define MAX             10000
#define CIN             ios_base::sync_with_stdio(0); cin.tie(0)
#define SZ(a)           (int)a.size()
#define sf(a)           scanf("%d",&a)
#define sff(a,b)        scanf("%d%d",&a,&b)
#define sfff(a,b,c)     scanf("%d%d%d",&a,&b,&c)
#define loop(i,n)       for(int i=0;i<n;i++)
#define REP(i,a,b)      for(int i=a;i<b;i++)
#define TEST_CASE(t)    for(int z=1;z<=t;z++)
#define PRINT_CASE      printf("Case %d:\n",z)
#define all(a)          a.begin(),a.end()
#define intlim          2147483648
#define inf             1000000
#define ull             unsigned long long

using namespace std;

struct data
{
int u,v,w;
bool operator< (const data& p)const
{
return w<p.w;
}
data(int x,int y, int z)
{
u=x,v=y,w=z;
}
};

vector<data>edge;
int n,m,cnt=0;
int par[210];

int find_par(int n)
{
return par[n]=(par[n]==n)?n:find_par(par[n]);
}

int mst()
{
int cnt=0,sum=0;
sort(all(edge));
vector<data>temp;
for(int i=0; i<SZ(edge); i++)
{
int u=find_par(edge[i].u);
int v=find_par(edge[i].v);
if(u!=v)
{
cnt++;
par[u]=v;
sum+=edge[i].w;
temp.pb(edge[i]);
if(cnt==n-1)
break;
}
}
edge.clear();
edge=temp;
if(cnt==n-1) return sum;
return -1;
}

int main()
{
///freopen("in.txt","r",stdin);
///freopen("out.txt","w",stdout);
int t;
sf(t);
TEST_CASE(t)
{
sff(n,m);
PRINT_CASE;
while(m--)
{
int x,y,z;
sfff(x,y,z);
edge.pb(data(x,y,z));
loop(i,n+5)
par[i]=i;
pf("%d\n",mst());
}
edge.clear();
}
return 0;
}

```

# Light OJ 1040 – Donation

0

Problem Link : http://www.lightoj.com/volume_showproblem.php?problem=1040

```
/*
+-+ +-+ +-+
|R| |.| |S|
+-+ +-+ +-+
*/

#include <bits/stdc++.h>

#define pii             pair <int,int>
#define sc              scanf
#define pf              printf
#define Pi              2*acos(0.0)
#define ms(a,b)         memset(a, b, sizeof(a))
#define pb(a)           push_back(a)
#define MP              make_pair
#define db              double
#define ll              long long
#define EPS             10E-10
#define ff              first
#define ss              second
#define sqr(x)          (x)*(x)
#define D(x)            cout<<#x " = "<<(x)<<endl
#define VI              vector <int>
#define DBG             pf("Hi\n")
#define MOD             100007
#define MAX             10000
#define CIN             ios_base::sync_with_stdio(0); cin.tie(0)
#define SZ(a)           (int)a.size()
#define sf(a)           scanf("%d",&a)
#define sff(a,b)        scanf("%d%d",&a,&b)
#define sfff(a,b,c)     scanf("%d%d%d",&a,&b,&c)
#define loop(i,n)       for(int i=0;i<n;i++)
#define REP(i,a,b)      for(int i=a;i<b;i++)
#define TEST_CASE(t)    for(int z=1;z<=t;z++)
#define PRINT_CASE      printf("Case %d: ",z)
#define all(a)          a.begin(),a.end()
#define intlim          2147483648
#define inf             1000000
#define ull             unsigned long long

using namespace std;

struct data
{
int u,v,w;
bool operator < (const data& p) const
{
return w<p.w;
}
data(int x,int y,int z)
{
u=x;
v=y;
w=z;
}
};

int par[MAX],test[MAX];
vector<data>edge;
int n;

int find_par(int n)
{
return par[n]= (par[n]==n)?n:find_par(par[n]);
}

int find_par_test(int n)
{
return test[n]= (test[n]==n)?n:find_par_test(test[n]);
}

int kruskal()
{
sort(all(edge));
int cost=0,cnt=0;
loop(i,SZ(edge))
{
int u=find_par(edge[i].u);
int v=find_par(edge[i].v);
if(u!=v)
{
par[u]=v;
cost+=edge[i].w;
cnt++;
if(cnt==n-1)
return cost;
}
}
}

void allclear()
{
loop(i,n+2)
{
test[i]=i;
par[i]=i;
}
edge.clear();
}

int main()
{
///freopen("in.txt","r",stdin);
///freopen("out.txt","w",stdout);
int t,c;
sf(t);
TEST_CASE(t)
{
sf(n);
allclear();
int total_cost=0;
loop(i,n) loop(j,n)
{
c=0;
sf(c);
if(c)
{
total_cost+=c;
edge.pb(data(i,j,c));
int a=find_par_test(i);
int b=find_par_test(j);
if(a!=b)
{
test[a]=b;
}
}
}
int cnt=0;
loop(i,n)
if(test[i]==i) cnt++;
PRINT_CASE;
if(cnt>1)
{
cout<<-1<<endl;
continue;
}
else
{
int temp=kruskal();
cout<<total_cost-temp<<endl;
}
}
return 0;
}

```

# Light OJ 1029 – Civil and Evil Engineer

0

Problem Link : http://www.lightoj.com/volume_showproblem.php?problem=1029

```
/*
+-+ +-+ +-+
|R| |.| |S|
+-+ +-+ +-+
*/

#include <bits/stdc++.h>

#define pii             pair <int,int>
#define sc              scanf
#define pf              printf
#define Pi              2*acos(0.0)
#define ms(a,b)         memset(a, b, sizeof(a))
#define pb(a)           push_back(a)
#define MP              make_pair
#define db              double
#define ll              long long
#define EPS             10E-10
#define ff              first
#define ss              second
#define sqr(x)          (x)*(x)
#define D(x)            cout<<#x " = "<<(x)<<endl
#define VI              vector <int>
#define DBG             pf("Hi\n")
#define MOD             100007
#define MAX             105
#define CIN             ios_base::sync_with_stdio(0); cin.tie(0)
#define SZ(a)           (int)a.size()
#define sf(a)           scanf("%d",&a)
#define sff(a,b)        scanf("%d%d",&a,&b)
#define sfff(a,b,c)     scanf("%d%d%d",&a,&b,&c)
#define loop(i,n)       for(int i=0;i<n;i++)
#define REP(i,a,b)      for(int i=a;i<b;i++)
#define TEST_CASE(t)    for(int z=1;z<=t;z++)
#define PRINT_CASE      printf("Case %d: ",z)
#define all(a)          a.begin(),a.end()
#define intlim          2147483648
#define inf             1000000
#define ull             unsigned long long

using namespace std;

struct data
{
int u,v,w;
data(int x,int y, int z){u=x,v=y,w=z;}
bool operator < (const data& p)const
{return w<p.w;}
};

int n;
vector<data>edge;
int par[MAX];

int find_par(int n)
{
return par[n]=(par[n]==n)?n:find_par(par[n]);
}

void allclear()
{
loop(i,n+2)
par[i]=i;
edge.clear();
}

int kruskal()
{
int sum=0,cnt=0;
for(int i=0;i<SZ(edge);i++)
{
int u=find_par(edge[i].u);
int v=find_par(edge[i].v);
if(u!=v)
{
cnt++;
par[u]=v;
sum+=edge[i].w;
if(cnt==n)
return sum;
}
}
}

int main()
{
///freopen("in.txt","r",stdin);
///freopen("out.txt","w",stdout);
int t;
sf(t);
TEST_CASE(t)
{
sf(n);
allclear();
int a,b,c;
while(sfff(a,b,c))
{
if(a==0 && b==0 && c==0) break;
edge.pb(data(a,b,c));
}
sort(all(edge));
int x=kruskal();
reverse(all(edge));
loop(i,n+2)
par[i]=i;
x+=kruskal();
PRINT_CASE;
if(x%2==0)
{
cout<<x/2<<endl;
}
else
cout<<x<<"/2"<<endl;
}
return 0;
}

```