java: add «2373. Largest Local Values in a Matrix»

Signed-off-by: Matej Focko <me@mfocko.xyz>

java/largest-local-values-in-a-matrix.java

@@ -0,0 +1,32 @@
+class Solution {
+  private boolean isValid(int n, int y, int x) {
+    return y >= 0 && y < n && x >= 0 && x < n;
+  }
+
+  private void addLocal(int[][] grid, int[][] result, int y, int x) {
+    for (int d = 0; d < 9; ++d) {
+      int dy = (d / 3) - 1;
+      int dx = (d % 3) - 1;
+
+      if (!isValid(grid.length - 2, y - 1 + dy, x - 1 + dx)) {
+        continue;
+      }
+
+      result[y - 1 + dy][x - 1 + dx] = Math.max(result[y - 1 + dy][x - 1 + dx], grid[y][x]);
+    }
+  }
+
+  public int[][] largestLocal(int[][] grid) {
+    int N = grid.length;
+    int[][] result = new int[N - 2][N - 2];
+
+    for (int i = 0; i < N * N; ++i) {
+      int y = i / N;
+      int x = i % N;
+
+      addLocal(grid, result, y, x);
+    }
+
+    return result;
+  }
+}