public static int findPeakElement(int[] num) {
        if (null == num || 0 == num.length) return -1; 
        int len = num.length;
        int low = 0, high = len - 1;
        int mid = 0;
        if (1 == len) return 0; 
        while (low < high) {
        	mid = (low + high) >> 1;
        	if (num[mid] < num[mid + 1]) low = mid + 1;
        	else high = mid;
        }
    	return low;
    }