MapSum (leetcode-in-java 1.23 API)

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 Description
  
  MapSum()
- Method Summary
  
  All Methods Instance Methods Concrete Methods
  Modifier and Type Method 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)
```