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/**

* Implement a MapSum class with insert, and sum methods.

*

* For the method insert, you'll be given a pair of (string, integer). The

* string represents the key and the integer represents the value. If the key

* already existed, then the original key-value pair will be overridden to

* the new one.

*

* For the method sum, you'll be given a string representing the prefix, and

* you need to return the sum of all the pairs' value whose key starts with

* the prefix.

*

* Example 1:

* Input: insert("apple", 3), Output: Null

* Input: sum("ap"), Output: 3

* Input: insert("app", 2), Output: Null

* Input: sum("ap"), Output: 5

*

*/

public class MapSumPairs677 {

class MapSum {

private Trie trie = new Trie();

/** Initialize your data structure here. */

public MapSum() {

}

public void insert(String key, int val) {

trie.add(key, val);

}

public int sum(String prefix) {

return trie.getSum(prefix);

}

class Trie {

Trie[] children = new Trie[256];

Integer value;

Integer sum = 0;

public void add(String key, int val) {

add(key.toCharArray(), val, 0);

}

private Integer add(char[] chars, int val, int i) {

if (i == chars.length) {

int diff = (value == null) ? val : val - value;

value = val;

sum += diff;

return diff;

}

int nextI = (int) (chars[i] - 'a');

if (children[nextI] == null) {

children[nextI] = new Trie();

}

Integer pre = sum;

Integer diff = children[nextI].add(chars, val, i+1);

sum = pre + diff;

return diff;

}

public int getSum(String prefix) {

int s = getSum(prefix.toCharArray(), 0);

return s;

}

private int getSum(char[] chars, int i) {

if (i == chars.length) return sum;

if (children[chars[i] - 'a'] == null) return 0;

return children[chars[i] - 'a'].getSum(chars, i+1);

}

}

}

class MapSum2 {

private Map<String, Integer> map = new HashMap<>();

private Trie trie = new Trie();

/** Initialize your data structure here. */

public MapSum() {

}

public void insert(String key, int val) {

int now = map.getOrDefault(key, 0);

trie.add(key, val - now);

map.put(key, val);

}

public int sum(String prefix) {

return trie.getSum(prefix);

}

class Trie {

Trie[] children = new Trie[256];

Integer sum = 0;

public void add(String key, int diff) {

add(key.toCharArray(), diff, 0);

}

private void add(char[] chars, int diff, int i) {

if (i == chars.length) {

sum += diff;

return;

}

int nextI = (int) (chars[i] - 'a');

if (children[nextI] == null) {

children[nextI] = new Trie();

}

sum += diff;

children[nextI].add(chars, diff, i+1);

}

public int getSum(String prefix) {

return getSum(prefix.toCharArray(), 0);

}

private int getSum(char[] chars, int i) {

if (i == chars.length) return sum;

if (children[chars[i] - 'a'] == null) return 0;

return children[chars[i] - 'a'].getSum(chars, i+1);

}

}

}

/**

* Your MapSum object will be instantiated and called as such:

* MapSum obj = new MapSum();

* obj.insert(key,val);

* int param_2 = obj.sum(prefix);

*/

}