递归和深度优先遍历

 

数组全排列

private void write(int[] b, ArrayList<ArrayList<Integer>> list,

                       LinkedList<Integer> item) {

        boolean flip;

        if (item.size() == b.length) {

            list.add(new ArrayList<Integer>(item));

            return;

        }

        for (int i = 0 ; i < b.length ; i++) {

            if (item.contains(b[i])) {

                continue;

            } else {

                item.add(b[i]);

                write(b, list, item);

                item.removeLast();

            }

        }

    }

 

深度优先搜索  先序遍历

public void dfs(TreeNode root) {

if (root != null) {

  System.out.print(root.val+" ");

  preOrderTraverse1(root.left);

  preOrderTraverse1(root.right);

}

深度优先搜索  中序遍历

public void dfs(TreeNode root) {

if (root != null) {

  preOrderTraverse1(root.left);

  System.out.print(root.val+" ");

  preOrderTraverse1(root.right);

}

深度优先搜索  后序遍历

public void dfs(TreeNode root) {

if (root != null) {

  preOrderTraverse1(root.left);

  preOrderTraverse1(root.right);

  System.out.print(root.val+" ");

}