g0601_0700.s0677_map_sum_pairs

Class MapSum

java.lang.Object

g0601_0700.s0677_map_sum_pairs.MapSum

public class MapSum
extends Object

677 - Map Sum Pairs.

Medium

Design a map that allows you to do the following:

• Maps a string key to a given value.
• Returns the sum of the values that have a key with a prefix equal to a given string.

Implement the MapSum class:

• MapSum() Initializes the MapSum object.
• void insert(String key, int val) Inserts the key-val pair into the map. If the key already existed, the original key-value pair will be overridden to the new one.
• int sum(string prefix) Returns the sum of all the pairs’ value whose key starts with the prefix.

Example 1:

Input

[“MapSum”, “insert”, “sum”, “insert”, “sum”] [[],

[“apple”, 3], [“ap”], [“app”, 2], [“ap”]]

Output: [null, null, 3, null, 5]

Explanation:

MapSum mapSum = new MapSum(); 
mapSum.insert("apple", 3); 
mapSum.sum("ap"); // return 3 (apple = 3) 
mapSum.insert("app", 2); 
mapSum.sum("ap"); // return 5 (apple + app = 3 + 2 = 5)

Constraints:

• 1 <= key.length, prefix.length <= 50
• key and prefix consist of only lowercase English letters.
• 1 <= val <= 1000
• At most 50 calls will be made to insert and sum.

Constructor Summary

Constructors

Constructor and Description
MapSum()

Method Summary

Modifier and Type	Method and Description
void	insert(String key, int val)
int	sum(String prefix)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

MapSum

public MapSum()

Method Detail

insert

public void insert(String key,
                   int val)

sum

public int sum(String prefix)