Bit Manipulation

• x >> 1
• x << 1
• x & 1
• reverse bit

    int hi = 31, lo = 0;
    while (hi > lo) {
            // swap bit
            int x = (n >> hi) & 1;
            int y = (n >> lo) & 1;
  
            if (x != y) {
                // use '^' to reverse bit
                n ^= (1 << hi) | (1 << lo);
            }
            hi--;
            lo++;
        }
  

• use bit to store multiple states to reduce space complexity
• use ‘^’ to seperate two number, find the first ‘1’ position
• condition check
  • (expression A) ^ (expressiion B), to check if two expressions has different results