Solution.ts

class FrequencyTracker {
    private cnt: Map<number, number>;
    private freq: Map<number, number>;

    constructor() {
        this.cnt = new Map();
        this.freq = new Map();
    }

    add(number: number): void {
        const f = this.cnt.get(number) || 0;
        this.freq.set(f, (this.freq.get(f) || 0) - 1);
        this.cnt.set(number, f + 1);
        this.freq.set(f + 1, (this.freq.get(f + 1) || 0) + 1);
    }

    deleteOne(number: number): void {
        const f = this.cnt.get(number) || 0;
        if (f > 0) {
            this.freq.set(f, (this.freq.get(f) || 0) - 1);
            this.cnt.set(number, f - 1);
            this.freq.set(f - 1, (this.freq.get(f - 1) || 0) + 1);
        }
    }

    hasFrequency(frequency: number): boolean {
        return (this.freq.get(frequency) || 0) > 0;
    }
}

/**
 * Your FrequencyTracker object will be instantiated and called as such:
 * var obj = new FrequencyTracker()
 * obj.add(number)
 * obj.deleteOne(number)
 * var param_3 = obj.hasFrequency(frequency)
 */