[20251123] BOJ / D5 / Hangar Hurdles / 권혁준

khj20006/202511/23 BOJ D5 Hangar Hurdles.md

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+```cpp
+#include <bits/stdc++.h>
+using namespace std;
+
+const int dx[4] = {1,0,-1,0};
+const int dy[4] = {0,1,0,-1};
+
+int N, Q;
+char arr[1001][1001]{};
+int srr[1001][1001]{};
+int cost[1000001]{}, root[1000001]{}, depth[1000001]{}, par[1000001][20]{}, val[1000001][20]{};
+
+vector<tuple<int, int, int>> edges;
+vector<vector<int>> v(1000001);
+
+int find(int x) { return x == root[x] ? x : root[x]=find(root[x]); }
+
+int sum(int x, int y, int xx, int yy) {
+    return srr[xx][yy] - srr[xx][y-1] - srr[x-1][yy] + srr[x-1][y-1];
+}
+
+void dfs(int n, int p, int d) {
+    par[n][0] = p, depth[n] = d;
+    for(int i:v[n]) if(i != p) {
+        dfs(i,n,d+1);
+        val[i][0] = cost[n];
+    }
+}
+
+int main(){
+    cin.tie(0)->sync_with_stdio(0);
+
+    cin>>N;
+    for(int i=1;i<=N;i++) for(int j=1;j<=N;j++) {
+        cin>>arr[i][j];
+        srr[i][j] = (arr[i][j] == '#' ? 1 : 0) + srr[i-1][j] + srr[i][j-1] - srr[i-1][j-1];
+    }
+
+    for(int i=1;i<=N;i++) for(int j=1;j<=N;j++) if(arr[i][j] != '#') {
+        int s = 0;
+        int e = min({abs(i-1), abs(N-i), abs(j-1), abs(N-j)});
+        int m = (s+e+1)>>1;
+        while(s<e) {
+            if(sum(i-m,j-m,i+m,j+m)) e = m-1;
+            else s = m;
+            m = (s+e+1)>>1;
+        }
+        cost[(i-1)*N+j] = 2*m+1;
+    }
+
+    for(int i=0;i<N;i++) for(int j=0;j<N;j++) {
+        for(int k=0;k<4;k++) {
+            int x = i+dx[k], y = j+dy[k];
+            if(x<0 || x>=N || y<0 || y>=N) continue;
+            int c = min(cost[i*N+j+1], cost[x*N+y+1]);
+            edges.emplace_back(c, i*N+j+1, x*N+y+1);
+        }
+    }
+
+    sort(edges.begin(), edges.end(), greater<>());
+    iota(root, root+N*N+1, 0);
+    for(auto [c,a,b] : edges) {
+        int x = find(a), y = find(b);
+        if(x == y) continue;
+        root[x] = y;
+        v[a].push_back(b);
+        v[b].push_back(a);
+    }
+
+    dfs(1,0,0);
+    for(int k=1;k<20;k++) for(int i=1;i<=N*N;i++) {
+        par[i][k] = par[par[i][k-1]][k-1];
+        val[i][k] = min(val[i][k-1], val[par[i][k-1]][k-1]);
+    }
+
+    for(cin>>Q;Q--;) {
+        int a,b,c,d;
+        cin>>a>>b>>c>>d;
+        int aa = (a-1)*N+b, bb = (c-1)*N+d;
+
+        int res = min(cost[aa], cost[bb]);
+        int diff = abs(depth[aa] - depth[bb]);
+        for(int k=0;k<20;k++) if(diff & (1<<k)) {
+            if(depth[aa] > depth[bb]) {
+                res = min(res, val[aa][k]);
+                aa = par[aa][k];
+            }
+            else {
+                res = min(res, val[bb][k]);
+                bb = par[bb][k];
+            }
+        }
+
+        for(int k=19;k>=0;k--) if(par[aa][k] != par[bb][k]) {
+            res = min({res, val[aa][k], val[bb][k]});
+            aa = par[aa][k];
+            bb = par[bb][k];
+        }
+        if(aa != bb) {
+            res = min({res, val[aa][0], val[bb][0]});
+        }
+
+        cout<<res<<'\n';
+    }
+
+}
+```