擅长:python、mysql、java
<p>希望这有帮助</p>
<pre><code>def addBefore(self, valueToFind, newNode):
currentNode = self.headval # point to headval
previousNode = None
while currentNode.data != valueToFind: # while currentNode.data is not equal to valueToFind, move currentNode to next node and keep track of previous node i.e. previousNode
previousNode = currentNode # keep tack of previous node
currentNode = currentNode.nextval # move to next node
previousNode.nextval = newNode # previous node will point to new node
previousNode = previousNode.nextval # move previous node to newly inserted node
previousNode.nextval = currentNode # previous node ka next will to currentNode
</code></pre>