feat: 实现基于0-1 BFS的最大欧式距离计算

添加0-1 BFS算法来计算网格中可达点的最小代价，并在此基础上计算满足条件的两点间最大欧式距离。主要功能包括：
- 实现0-1 BFS算法计算各点到起点的最小代价
- 遍历所有点对，筛选满足代价条件的点对
- 计算并输出最大欧式距离

src/10/1/P4162.cpp

@@ -1,3 +1,89 @@
-int main(){
+#include <cstdio>
+#include <iostream>
+#include <vector>
+#include <deque>
+#include <cmath>
+#include <iomanip>
+#include <algorithm>
+using namespace std;
+
+const int MAXN = 35;
+const int dx[4] = {0, 1, 0, -1};
+const int dy[4] = {1, 0, -1, 0};
+
+int n, m, T;
+char grid[MAXN][MAXN];
+
+bool isValid(int x, int y) {
+    return x >= 0 && x < n && y >= 0 && y < m;
+}
+
+vector<vector<int>> bfs01(int sx, int sy) {
+    vector<vector<int>> dist(n, vector<int>(m, 0x3f3f3f3f));
+    vector<vector<bool>> visited(n, vector<bool>(m, false));
+    deque<pair<int, int>> dq;
     
-}
+    int startcost = (grid[sx][sy] == '1') ? 1 : 0;
+    dist[sx][sy] = startcost;
+    dq.push_back({sx, sy});
+    
+    while (!dq.empty()) {
+        auto [x, y] = dq.front();
+        dq.pop_front();
+        
+        if (visited[x][y]) continue;
+        visited[x][y] = true;
+        
+        for (int i = 0; i < 4; i++) {
+            int nx = x + dx[i];
+            int ny = y + dy[i];
+            
+            if (!isValid(nx, ny)) continue;
+            
+            int cost = (grid[nx][ny] == '1') ? 1 : 0;
+            if (dist[x][y] + cost < dist[nx][ny]) {
+                dist[nx][ny] = dist[x][y] + cost;
+                if (cost == 0) {
+                    dq.push_front({nx, ny});
+                } else {
+                    dq.push_back({nx, ny});
+                }
+            }
+        }
+    }
+    
+    return dist;
+}
+
+double euladis(int x1, int y1, int x2, int y2) {
+    return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
+}
+
+int main() {
+    ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+    
+    cin >> n >> m >> T;
+    
+    for (int i = 0; i < n; i++) {
+        for (int j = 0; j < m; j++) {
+            cin >> grid[i][j];
+        }
+    }
+    
+    double maxdis = 0.0;
+    
+    for (int i = 0; i < n; i++) {
+        for (int j = 0; j < m; j++) {
+            auto dist = bfs01(i, j);
+            for (int x = 0; x < n; x++) {
+                for (int y = 0; y < m; y++) {
+                    if (dist[x][y] <= T) {
+                        maxdis = max(maxdis, euladis(i, j, x, y));
+                    }
+                }
+            }
+        }
+    }
+    printf("%.6f\n", maxdis);
+}