LeetCode Find Peak Element [TBD]

class Solution {
public:
    int findPeakElement(const vector<int> &num) {
        int len = num.size();
        if (len < 1) {
            return -1;
        }
        if (len == 1) {
            return 0;
        }
        bool asc = true;
        int idx = 0;
        int last = num[idx++];
        
        while (idx < len) {
            int cur = num[idx];
            if (asc) {
                if (cur < last) {
                    return idx - 1;
                }
            } else {
                if (cur > last) {
                    asc = true;   
                }
            }
            last = cur;
            idx++;
        }
        if (asc) {
            return idx - 1;
        }
        return -1;
    }
};