Solution.ts

class Trie {
    children: Trie[];
    val: number;

    constructor() {
        this.children = new Array(26);
        this.val = 0;
    }

    insert(w: string, x: number) {
        let node: Trie = this;
        for (const c of w) {
            const i = c.charCodeAt(0) - 97;
            if (!node.children[i]) {
                node.children[i] = new Trie();
            }
            node = node.children[i];
            node.val += x;
        }
    }

    search(w: string): number {
        let node: Trie = this;
        for (const c of w) {
            const i = c.charCodeAt(0) - 97;
            if (!node.children[i]) {
                return 0;
            }
            node = node.children[i];
        }
        return node.val;
    }
}

class MapSum {
    d: Map<string, number>;
    t: Trie;
    constructor() {
        this.d = new Map();
        this.t = new Trie();
    }

    insert(key: string, val: number): void {
        const x = val - (this.d.get(key) ?? 0);
        this.d.set(key, val);
        this.t.insert(key, x);
    }

    sum(prefix: string): number {
        return this.t.search(prefix);
    }
}

/**
 * Your MapSum object will be instantiated and called as such:
 * var obj = new MapSum()
 * obj.insert(key,val)
 * var param_2 = obj.sum(prefix)
 */