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Author: MishkatIT

2812-find-the-safest-path-in-a-grid/2812-find-the-safest-path-in-a-grid.cpp

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+class Solution {
+public:
+    int maximumSafenessFactor(vector<vector<int>>& grid) {
+        
+        int n = grid.size();
+        
+        vector<vector<int>> safeness(n, vector<int>(n, 1e9));
+
+        int dy[4] = {0, 0, 1, -1};
+        int dx[4] = {-1, 1, 0, 0};
+
+        queue<pair<int, int>> q;
+        for (int i = 0; i < n; i++) {
+            for (int j = 0; j < n; j++) {
+                if (grid[i][j] == 1) {
+                    safeness[i][j] = 0;
+                    q.push({i, j});
+                }
+            }
+        }
+
+        while (!q.empty()) {
+            auto cur = q.front();
+            q.pop();
+            int x = cur.first, y = cur.second;
+            for (int d = 0; d < 4; d++) {
+                int nx = x + dx[d];
+                int ny = y + dy[d];
+                if (nx >= 0 && nx < n && ny >= 0 && ny < n &&
+                    safeness[nx][ny] > safeness[x][y] + 1) {
+                    safeness[nx][ny] = safeness[x][y] + 1;
+                    q.push({nx, ny});
+                }
+            }
+        }
+        priority_queue<array<int, 3>> pq;
+        pq.push({safeness[0][0], 0, 0});
+        vector<vector<bool>> vis(n, vector<bool>(n, false));
+        while (!pq.empty()) {
+            auto cur = pq.top();
+            pq.pop();
+            vis[cur[1]][cur[2]] = true;
+            if (cur[1] == n - 1 && cur[2] == n - 1)
+                return cur[0];
+            for (int d = 0; d < 4; d++) {
+                int nx = cur[1] + dx[d], ny = cur[2] + dy[d];
+                if (nx >= 0 && nx < n && ny >= 0 && ny < n && !vis[nx][ny]) {
+                    pq.push({min(cur[0], safeness[nx][ny]), nx, ny});
+                }
+            }
+        }
+        return 0;
+    }
+};