421. maximum XOR value of two numbers in the array

Prefix tree idea

https://www.youtube.com/watch?v=wSgrc98d2lI

Suppose there is 5 A digital , Binary is as follows :

• 00010
• 00101
• 01000
• 01010
• 11001
  Store them in the prefix tree as shown in the following figure .
  
  Every time , We look at a number , Look from high to low , From all the choices, find the number that can form the maximum XOR result with him .

Pictured above , Let's look at the numbers first 11001, Try to find the best match for him .

1. The highest position is 1, If the high order of another number is 0, Can form the maximum result . The root node of the prefix tree has 0 Child node , So we came to 0.
2. So is the second 1, So select another from the child nodes 0.
3. The third is 0, The third best match is 1, So we went to 1 Child node .
4. And so on , When looking up the prefix tree , Choose the best child nodes first , If it doesn't , Just choose another one .

Finally, the calculation result of the best match is returned .