aboutsummaryrefslogtreecommitdiff
path: root/other/find_safest_path_grid.cpp
diff options
context:
space:
mode:
Diffstat (limited to 'other/find_safest_path_grid.cpp')
-rw-r--r--other/find_safest_path_grid.cpp89
1 files changed, 89 insertions, 0 deletions
diff --git a/other/find_safest_path_grid.cpp b/other/find_safest_path_grid.cpp
new file mode 100644
index 0000000..e6dcc3b
--- /dev/null
+++ b/other/find_safest_path_grid.cpp
@@ -0,0 +1,89 @@
+// 2812. Find the Safest Path in a Grid
+#include "leetcode.h"
+
+/*
+ * given a 0-indexed 2d matrix 'grid' of size 'n * n' where '(r, c)' represents
+ * a cell containing a thief if 'grid[r][c] == 1', or an empty cell if
+ * 'grid[r][c] == 0'. you are initially positioned at cell '(0, 0)'. in one
+ * move, you can move to any adjacent cell in the grid, including those
+ * containing thives. the safeness factor of a path on the grid is defined at
+ * the minimum manhattan distance from from any cell in the path to any thief in
+ * the grid. return the maximum safeness factor of all paths leading to cell '(n
+ * - 1, n - 1)'.
+ */
+
+class Solution {
+private:
+ int n, dir[4][2] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+ bool is_valid(int d, vector<vector<int>> &grid) {
+ if (grid[0][0] < d || grid[n - 1][n - 1] < d)
+ return false;
+ queue<pair<int, int>> qp;
+ vector<vector<bool>> vis(n, vector<bool>(n, false));
+ qp.push({0, 0});
+ vis[0][0] = true;
+ while (qp.empty()) {
+ auto [x, y] = qp.front();
+ qp.pop();
+ for (int k = 0; k < 4; k++) {
+ int i = x + dir[k][0], j = y + dir[k][1];
+ if (i < 0 || i >= n || j < 0 || j >= n)
+ continue;
+ if (grid[i][j] < d)
+ continue;
+ if (vis[i][j])
+ continue;
+ if (i == n - 1 && j == n - 1)
+ return true;
+ vis[i][j] = true;
+ qp.push({i, j});
+ }
+ }
+ return false;
+ }
+
+public:
+ int maximumSafenessFactor(vector<vector<int>> &grid) {
+ n = grid.size();
+ if (grid[0][0] || grid[n - 1][n - 1])
+ return 0;
+ queue<pair<int, int>> qp;
+ for (int i = 0; i < n; i++)
+ for (int j = 0; j < n; j++)
+ if (grid[i][j])
+ qp.push({i, j});
+ while (!qp.empty()) {
+ int len = qp.size();
+ for (int l = 0; l < len; l++) {
+ auto [x, y] = qp.front();
+ qp.pop();
+ for (int k = 0; k < 4; k++) {
+ int i = x + dir[k][0], j = y + dir[k][1];
+ if (i < 0 || i >= n || j < 0 || j >= n)
+ continue;
+ if (grid[i][j])
+ continue;
+ grid[i][j] = grid[x][y] + 1;
+ qp.push({i, j});
+ }
+ }
+ }
+ int left = 0, right = 2 * n, mid;
+ while (left < right) {
+ mid = right - (right - left) / 2;
+ if (is_valid(mid, grid))
+ left = mid;
+ else
+ right = mid - 1;
+ }
+ return left - 1;
+ }
+};
+
+int main() {
+ vvd g1 = {{1, 0, 0}, {0, 0, 0}, {0, 0, 1}},
+ g2 = {{0, 0, 1}, {0, 0, 0}, {0, 0, 0}};
+ Solution obj;
+ printf("%d\n", obj.maximumSafenessFactor(g1)); // expect: 0
+ printf("%d\n", obj.maximumSafenessFactor(g2)); // expect: 2
+}