Solution.ts

class BinaryIndexedTree {
    private n: number;
    private c: number[];

    constructor(n: number) {
        this.n = n;
        this.c = Array(n + 1).fill(0);
    }

    update(x: number, delta: number): void {
        for (; x <= this.n; x += x & -x) {
            this.c[x] += delta;
        }
    }

    query(x: number): number {
        let s = 0;
        for (; x > 0; x -= x & -x) {
            s += this.c[x];
        }
        return s;
    }
}

class StreamRank {
    private tree: BinaryIndexedTree = new BinaryIndexedTree(50010);

    constructor() {}

    track(x: number): void {
        this.tree.update(x + 1, 1);
    }

    getRankOfNumber(x: number): number {
        return this.tree.query(x + 1);
    }
}

/**
 * Your StreamRank object will be instantiated and called as such:
 * var obj = new StreamRank()
 * obj.track(x)
 * var param_2 = obj.getRankOfNumber(x)
 */