USACO 2.3 Controlling Companies (concom)

//Main Idea:
//brute force;
//shares[i][j] is the initial shares company i own for company j;
//fianl_shares[i][j] is the shares company i own for j after calculate;
//used[i][j] == 1 denote i control j to avoid repeated computation;

/*
ID: haolink1
PROG: concom
LANG: C++
*/

//#include <iostream>
#include <fstream>

using namespace std;

const int com = 100;
short shares[com][com],final_shares[com][com];
bool  used[com][com];

int main(){
ifstream fin("concom.in");
int num = 0;
fin >> num;
int com_1 = 0; int com_2 = 0;
for(int i = 0; i < num ; i++){
fin >> com_1 >> com_2;
fin >> shares[com_1-1][com_2-1];
final_shares[com_1-1][com_2-1] = shares[com_1-1][com_2-1];
}

bool flag = 1;
while(flag){
flag = 0;
for(int i = 0; i < com; i++){
for(int j = 0; j < com; j++){
if(used[i][j] == 0 && final_shares[i][j] > 50 && i != j){
//used[i][j] = used[j][i] = 1;
used[i][j] = 1;
flag = 1;
for(int k = 0; k < com; k++){
if(k != i && k != j)// now company i got company k's share that j own;
final_shares[i][k] += shares[j][k];
}
}
}
}
}
flag = 1;
ofstream fout("concom.out");
for(int i = 0; i < com; i++){
for(int j = 0; j < com; j++){
if(final_shares[i][j] > 50 && i != j){
fout<< i+1 <<" "<< j+1 << endl;
flag = 0;
}
}
}
if(flag)
fout << 0 << endl;
return 0;
}