vector<pair<int, int> > getMatch(V2D vX, V2D vY) {
X = vX;
Y = vY;
SZ = X.size();
for(int i = 0; i < SZ; ++i)
for(int j = 0; j < SZ; ++j)
Y[i][vY[i][j]] = j;
mX.assign(SZ, -1);
mY.assign(SZ, -1);
k.assign(SZ, 0);
bool yes = true;
while(true) {
bool mark = true;
int i;
for(i = 0; i < SZ; ++i) {
if(mX[i] == -1) {
while(k[i] < SZ) {
int j = X[i][k[i]];
if( mY[j] == -1 ) {
mX[i] = j;
mY[j] = i;
break;
}
if( Y[j][i] < Y[j][mY[j]] ) {
mX[mY[j]] = -1;
k[mY[j]]++;
mX[i] = j;
mY[j] = i;
break;
}
++k[i];
}
if(mX[i] == -1)
mark = false;
break;
}
}
if(i == N)
break;
if(!mark) {
yes = false;
break;
}
}
vector<pair<int, int> > ans(0);
if(!yes) return ans;
for(int i = 0; i < SZ; ++i)
ans.push_back(make_pair(i, mX[i]));
return ans;
}
