Maximum Difference Between Increasing Elements

<-E 2016> Maximum Difference Between Increasing Elements

class Solution {
public:
    int maximumDifference(vector<int>& nums) {
        int result = 0, prefix = INT_MAX;
        for (auto x : nums) {
            result = max(result, x - prefix);
            prefix = min(prefix, x);
        }
        return result ? result : -1;
    }
};