2166. Design Bitset

T: toString(): O(n), others are all O(1)

S: O(n)

class Bitset {

    int size;
    Set<Integer> one;
    Set<Integer> zero;
    public Bitset(int size) {
        this.size = size;
        one = new HashSet<>();
        zero = new HashSet<>();
        for (int i = 0; i < size; i++) {
            zero.add(i);
        }
    }
    
    public void fix(int idx) {
        one.add(idx);
        zero.remove(idx);
    }
    
    public void unfix(int idx) {
        one.remove(idx);
        zero.add(idx);
    }
    
    public void flip() {
        Set<Integer> temp = one;
        one = zero;
        zero = temp;
    }
    
    public boolean all() {
        // all values of the bitset are 1. return true
        return one.size() == size;
    }
    
    public boolean one() {
        return one.size() > 0;
    }
    
    public int count() {
        return one.size();
    }
    
    public String toString() {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < size; i++) {
            if (one.contains(i)) {
                sb.append("1");
            } else {
                sb.append("0");
            }
        }
        return sb.toString();
    }
}

/**
 * Your Bitset object will be instantiated and called as such:
 * Bitset obj = new Bitset(size);
 * obj.fix(idx);
 * obj.unfix(idx);
 * obj.flip();
 * boolean param_4 = obj.all();
 * boolean param_5 = obj.one();
 * int param_6 = obj.count();
 * String param_7 = obj.toString();
 */

use bit operarion

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