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#ifdef LOCAL
#include <bits/stdc++.h>
using namespace std;
// tree node stuff here...
#endif
static int __initialSetup = []()
{
std::ios::sync_with_stdio(false);
cin.tie(NULL);
return 0;
}
();
// handle special cases first
// [], "", ...
// range of input?
typedef pair<int, int> ii;
class Solution
{
private:
const int dx[4] = {0, 0, 1, -1};
const int dy[4] = {1, -1, 0, 0};
bool ok(int x, int y, int n, int m)
{
return (0 <= x && x < n) && (0 <= y && y < m);
}
void bfs(vector<vector<int>> &grid, vector<vector<int>> &dp,
vector<vector<int>> &cnt, int n, int m, int x, int y)
{
queue<ii> q;
map<ii, int> inqueue;
q.push(ii(x, y));
inqueue[ii(x, y)] = 0;
while (q.size() > 0) {
ii cur = q.front();
q.pop();
int level = inqueue[cur];
dp[cur.first][cur.second] += level;
for (int i = 0; i < 4; i++) {
int xx = cur.first + dx[i];
int yy = cur.second + dy[i];
if (ok(xx, yy, n, m) && inqueue.count(ii(xx, yy)) == 0 &&
grid[xx][yy] == 0) {
q.push(ii(xx, yy));
inqueue[ii(xx, yy)] = level + 1;
cnt[xx][yy]++;
}
}
}
}
public:
int shortestDistance(vector<vector<int>> &grid)
{
int n = grid.size();
int m = grid[0].size();
vector<vector<int>> dp(n, vector<int>(m, 0));
vector<vector<int>> cnt(n, vector<int>(m, 0));
// cal dp
int buildings = 0;
for (int i = 0; i < n; i++)
for (int j = 0; j < m; j++)
if (grid[i][j] == 1) {
bfs(grid, dp, cnt, n, m, i, j);
buildings++;
}
// get answer
int mn = INT_MAX;
for (int i = 0; i < n; i++)
for (int j = 0; j < m; j++) {
if (grid[i][j] == 0 && cnt[i][j] == buildings)
mn = min(mn, dp[i][j]);
}
return mn == INT_MAX ? -1 : mn;
}
};
#ifdef LOCAL
int main()
{
return 0;
}
#endif
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