Class Pair

java/0920-number-of-music-playlists.java:36–57

    }

    class Pair {
        int a;
        int b;

        public Pair(int a, int b) {
            this.a = a;
            this.b = b;
        }

        @Override
        public boolean equals(Object obj) {
            if (this == obj) return true;
            if (obj == null || getClass() != obj.getClass()) return false;
            Pair pair = (Pair) obj;
            return a == pair.a && b == pair.b;
        }

        @Override
        public int hashCode() {
            return 31 * a + b;
        }
    }
}