Single Number 系列

经典题目

a .length == n, one appear once and others appear 2 times. Find the one.

异或消除法：a ^ a = 0

136 Single Number

// T/O(n), S/O(1)
public int singleNumber(int[] nums) {
    int ans = 0;
    for (int num : nums) {
        ans ^= num;
    }
    return ans;
}

a.length == n, one appear once and others appear 3 times. Find the one.

137 Single Number II

// T/O(n), S/O(1)

a.length == n, two appear once and others appear 2 times. Find the one.

260 Single Number III

// T/O(n), S/O(1)