github.com/searKing/golang/go@v1.2.117/container/traversal/postorder.go (about)

     1  // Copyright 2020 The searKing Author. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // https://en.wikipedia.org/wiki/Tree_traversal#Post-order_(LRN)
     6  package traversal
     7  
     8  // Post-order (LRN)
     9  // 1. Check if the current node is empty or null.
    10  // 2. Traverse the left subtree by recursively calling the post-order function.
    11  // 3. Traverse the right subtree by recursively calling the post-order function.
    12  // 4. Display the data part of the root (or current node).
    13  // Implement:
    14  // 	postorder(node)
    15  // 		if (node = null)
    16  // 			return
    17  // 		postorder(node.left)
    18  // 		postorder(node.right)
    19  // 		visit(node)
    20  
    21  // TODO template in Go2.0 is expected
    22  // Postorder traversals from node ele by Post-order (LRN)
    23  // ele is a node which may have some interfaces implemented:
    24  // LeftNodes|MiddleNodes|RightNodes
    25  func Postorder(node any, handler Handler) {
    26  	traversal(node, traversalerFunc(postorder), handler)
    27  }
    28  
    29  func postorder(currents []levelNode, handler levelNodeHandler) (goon bool) {
    30  	if len(currents) == 0 {
    31  		return true
    32  	}
    33  	// Step 1: brothers
    34  	for _, node := range currents {
    35  		if node.visited {
    36  			continue
    37  		}
    38  		// process children
    39  		if !outorder(node.leftLevelNodes(), handler) {
    40  			return false
    41  		}
    42  		if !outorder(node.rightLevelNodes(), handler) {
    43  			return false
    44  		}
    45  		// process root
    46  		if !handler.Handle(node) {
    47  			return false
    48  		}
    49  		// process children
    50  		if !outorder(node.middleLevelNodes(), handler) {
    51  			return false
    52  		}
    53  	}
    54  	return true
    55  }