  Controlling a complex network is of great importance in many applications.
The network can be controlled by inputting external control signals through
some selected nodes, which are called input nodes. Previous works found that
the majority of the nodes in dense networks are either the input nodes or not,
which leads to the bimodality in controlling the complex networks. Due to the
physical or economic constraints of many real control scenarios, altering the
control mode of a network may be critical to many applications. Here we develop
a graph-based algorithm to alter the control mode of a network. The main idea
is to change the control connectivity of nodes by removing carefully selected
edges. We rigorously prove the correctness of our algorithm and evaluate its
performance on both synthetic and real networks. The experimental results show
that the control mode of a network can be easily changed by removing few
selected edges. Our methods provide the ability to design the desired control
mode for different control scenarios, which may be useful in many applications.
