public int numIslands(char[][] grid) {
int counter = 0;
int n = grid.length;
if (n == 0) return 0;
int m = grid[0].length;
if (m == 0) return 0;
int[][] direct = new int[][] {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
if (grid[i][j] == '1') {
counter++;
ArrayDeque<Integer> q = new ArrayDeque<Integer>();
grid[i][j] = 0;
q.add(i);
q.add(j);
while (!q.isEmpty()) {
int r = q.poll();
int c = q.poll();
for (int[] d : direct) {
int rr = d[0] + r;
int cc = d[1] + c;
if (rr >= 0 && rr < n && cc >= 0 && cc < m && grid[rr][cc] == '1') {
grid[rr][cc] = 0;
q.add(rr);
q.add(cc);
}
}
}
}
}
}
return counter;
}
public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
List<List<Integer>> r = new ArrayList<List<Integer>>();
ArrayDeque<TreeNode> q = new ArrayDeque<TreeNode>();
if (root == null) return r;
q.offer(root);
boolean reversedOrder = false;
while (!q.isEmpty()) {
int len = q.size();
List<Integer> level = new LinkedList<Integer>();
for (int i = 0; i < len; i++) {
TreeNode n = q.poll();
if (reversedOrder) level.add(0, n.val);
else level.add(n.val);
if (n.left != null) q.offer(n.left);
if (n.right != null) q.offer(n.right);
}
r.add(level);
reversedOrder = !reversedOrder;
}
return r;
}
