找出一个子树，使之结点的数值之和为最大！
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1 class tree_node(object): 2 """docstring for TreeNode""" 3 def __init__(self,val,left = None,right = None): 4 self.val = val 5 self.left = left 6 self.right = right 7 8 9 class attr_of_tree(object): 10 """docstring for list_node """ 11 def __init__(self,is_positive,sum,root): 12 self.is_positive = is_positive 13 self.sum = sum 14 self.root = root 15 16 17 18 def get_max_sub_tree(root,flag = False): 19 20 def f(root,l): 21 if root is None: 22 return attr_of_tree(True,0,root) 23 else: 24 left = f(root.left,l) 25 right = f(root.right,l) 26 attr = attr_of_tree(left.is_positive and right.is_positive and root.val > 0 , left.sum + right.sum + root.val , root) 27 l.append(attr) 28 return attr 29 30 l = [] 31 f(root,l) 32 if flag: 33 l = [i for i in l if i.is_positive] 34 return max(l,key = lambda x: x.sum).root 35 36 37 38 def build_test_tree(l): 39 40 def f(l,n): 41 if n > len(l)-1 or l[n] is None: 42 return None 43 else : 44 return tree_node(l[n],f(l,2*n+1),f(l,2*n+2)) 45 46 return f(l,0) 47 48 49 def print_tree(root): 50 if root is None: 51 return 52 else: 53 print root.val 54 print_tree(root.left) 55 print_tree(root.right) 56 57 58 59 def main(): 60 root = build_test_tree( [0,-7,2,3,4,-4,3,4] ) 61 print "==========================" 62 ret = get_max_sub_tree(root) 63 print_tree(ret) 64 65 root = build_test_tree( [0,-10,2,3,4,1,3,4,-1] ) 66 print "==========================" 67 ret = get_max_sub_tree(root) 68 print_tree(ret) 69 70 root = build_test_tree( [0,-10,2,3,4,1,3,4,-1] ) 71 print "==========================" 72 ret = get_max_sub_tree(root,True) 73 print_tree(ret) 74 75 76 77 78 79 80 if __name__ == '__main__': 81 main()