Add Graphs subfolder

Author: Sean Prashad

Tree Breadth First Search/133_Clone_Graph.java renamed to Graphs/133_Clone_Graph.java

@@ -0,0 +1,50 @@
+class Solution {
+ public List<List<Integer>> pacificAtlantic(int[][] matrix) {
+ if (matrix == null || matrix.length == 0) {
+ return Collections.emptyList();
+ }
+
+ List<List<Integer>> result = new ArrayList<>();
+ int rows = matrix.length, cols = matrix[0].length;
+
+ boolean[][] pacificVisited = new boolean[rows][cols];
+ boolean[][] atlanticVisited = new boolean[rows][cols];
+
+ for (int i = 0; i < rows; i++) {
+ dfs(matrix, i, 0, -1, pacificVisited);
+ dfs(matrix, i, cols - 1, -1, atlanticVisited);
+ }
+
+ for (int j = 0; j < cols; j++) {
+ dfs(matrix, 0, j, -1, pacificVisited);
+ dfs(matrix, rows - 1, j, -1, atlanticVisited);
+ }
+
+ for (int i = 0; i < rows; i++) {
+ for (int j = 0; j < cols; j++) {
+ if (pacificVisited[i][j] && atlanticVisited[i][j]) {
+ result.add(Arrays.asList(i, j));
+ }
+ }
+ }
+
+ return result;
+ }
+
+ private void dfs(int[][] matrix, int x, int y, int prevWaterHeight, boolean[][] visited) {
+ if (x < 0 || y < 0 || x >= matrix.length || y >= matrix[x].length || visited[x][y]
+ || prevWaterHeight > matrix[x][y]) {
+ return;
+ }
+
+ int height = matrix[x][y];
+ visited[x][y] = true;
+
+ dfs(matrix, x - 1, y, height, visited);
+ dfs(matrix, x + 1, y, height, visited);
+ dfs(matrix, x, y - 1, height, visited);
+ dfs(matrix, x, y + 1, height, visited);
+
+ return;
+ }
+}