706. Design HashMap

class ListNode:
    def __init__(self,key,val):
        self.pair = (key,val)
        self.next = None 

class MyHashMap:
    """main idea: chaining 
    """
    def __init__(self):
        self.m = 1000
        self.table = [None]*self.m
   

    def put(self, key: int, value: int) -> None:
        """
        value will always be non-negative.
        1. get hcode 
        2. check if self.table[h] empty:  if yes, plug  otherwise, find the exact key and update value. if no same key found, plug in the end         
        """
        h = key%self.m
        if not self.table[h] :
            self.table[h] = ListNode(key,value)
            return 
        node = self.table[h]
        prev = None 
        while node:
            if node.pair[0] == key:
                node.pair = (key,value)
                return
            prev = node 
            node = node.next
        prev.next = ListNode(key, value)
        
        
        

    def get(self, key: int) -> int:
        """
        Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key
        1. get hcode
        2. check all keys at hcode position until find exact key
        """
        h = key % self.m
        if not self.table[h]:
            return -1
        node = self.table[h]
        while node:
            if node.pair[0] == key:
                return node.pair[1]
            node = node.next 
        return -1 

    def remove(self, key: int) -> None:
        """
        Removes the mapping of the specified value key if this map contains a mapping for the key
        1. get hcode
        2. chekc if head's key is target key:  yes -> leave second listnode as head; no -> loop until find the exact node with the same key; meanwhile save current node's prev node until remove current node 
        """
        h = key % self.m 
        if not self.table[h]:
            return 
        node = self.table[h]
        if node.pair[0] == key:
            self.table[h] = node.next
            return 
        prev = node 
        while node:
            if node.pair[0] == key:
                prev.next = node.next
                return 
            prev = node
            node = node.next
        
        


# Your MyHashMap object will be instantiated and called as such:
# obj = MyHashMap()
# obj.put(key,value)
# param_2 = obj.get(key)
# obj.remove(key)