class Solution {
public:
    int bagOfTokensScore(vector<int>& tokens, int P) {
        sort(tokens.begin(),tokens.end());
        int left = 0, right = tokens.size() - 1;
        int points = 0, ans = 0;
        while (left <= right && (P >= tokens[left] || points > 0)) {
            while (left <= right && P >= tokens[left]) {
                P -= tokens[left++];
                points++;
            }
            ans = max(ans, points);
            if (left <= right && points > 0) {
                P += tokens[right--];
                points--;
            }
        }
        return ans;
    }
};