void _Solve(){
int maxSafePls = 0;
FOR_DEC(border, 0, m_max+1) {
const int numSafePls = CountSafePls(m_grid, border);
if (numSafePls > maxSafePls) {
maxSafePls = numSafePls;
}
}
cout << maxSafePls;
} // _Solve()
int CountSafePls(vvi grid, const int border) {
vii viiTops = PickStartingPts(grid, border);
typedef pair<int, ii> i_ii;
queue<i_ii> i_iiQ;
FOR (i, viiTops.size()) {
i_iiQ.push(i_ii(i+1, viiTops[i]));
}
const int maxLoop = INF;
for (int i=0; !i_iiQ.empty() && i<maxLoop; ++i) {
const i_ii cnt_pos = i_iiQ.front(); i_iiQ.pop();
const int cnt = cnt_pos.first;
const ii pos = cnt_pos.second;
if (Visit(grid, border, pos, cnt)) {
FOR (dir, eDIR_LEN) {
const ii nextPos = ii( pos.first + DIR[dir][0],
pos.second + DIR[dir][1]);
if (OOR(nextPos.first, 0, m_N-1)) { continue; }
if (OOR(nextPos.second, 0, m_N-1)) { continue; }
const int val = grid[nextPos.first][nextPos.second];
if (val <= -1*cnt) { continue; }
i_iiQ.push(i_ii(cnt, nextPos));
}
}
}
unordered_set<int> hashCnt;
FOR (r, m_N) {
FOR (c, m_N) {
const int val = grid[r][c];
if (val < 0) {
hashCnt.insert(val);
}
}
}
return hashCnt.size();
}
bool Visit(vvi& grid, const int border, const ii& pos, const int cnt) {
if (OOR(pos.first, 0, m_N)) return false;
if (OOR(pos.second, 0, m_N)) return false;
const int val = grid[pos.first][pos.second];
if (val >= border) {
grid[pos.first][pos.second] = -1*cnt;
return true;
}
else if ((val < 0) && (val > -1*cnt)) {
// Update with smaller value (bigger count)
grid[pos.first][pos.second] = -1*cnt;
return true;
}
else if (val <= -1*cnt) {
return false;
}
else {}
}
vii PickStartingPts(const vvi& grid, const int border) {
vii viiTops;
FOR (r, m_N) {
FOR (c, m_N) {
const int val = grid[r][c];
if (val >= border) {
viiTops.push_back(ii(r,c));
}
}
}
return viiTops;
}
void PrintGrid(const vvi& grid) {
cout <<endl;
FOR(i, m_N){
FOR(j, m_N){
cout << setw(3) << grid[i][j] << " ";
}
cout <<endl;
}
}
