旋转数组的最小数字

    private int minNumberInRotateArray(int [] array) {
        if (array == null || array.length == 0) {
            throw new RuntimeException("input is invalid");
        }

        int index1 = 0;
        int index2 = array.length-1;
        int indexMid = index1;
        while (array[index1] >= array[index2]) {
            if (index2 - index1 == 1) {
                indexMid = index2;
            }
            
            indexMid = (index1 + index2)/2;
            if (array[indexMid] >= array[index2]) {
                index1 = indexMid;
            } else {
                index2 = indexMid;
            }
        }
        
        return array[indexMid];
    }