You have an initial power P, an initial score of 0 points, and a
bag of tokens.
Each token can be used at most once, has a value token[i], and has potentially
two ways to use it.
token[i] power, we may play the token face up, losing
token[i] power, and gaining 1 point.
1 point, we may play the token face down, gaining
token[i] power, and losing 1 point.
Return the largest number of points we can have after playing any number of tokens.
Example 1:
Input: tokens = [100], P = 50 Output: 0
Example 2:
Input: tokens = [100,200], P = 150 Output: 1
Example 3:
Input: tokens = [100,200,300,400], P = 200 Output: 2
Note:
tokens.length <= 10000 <= tokens[i] < 100000 <= P < 10000