Zhenhua Lyu

collaborators

4 papers

math.CO2021

A note on extremal digraphs containing at most $t$ walks of length $k$ with the same endpoints

Zhenhua Lyu

Let $n, k, t$ be positive integers. What is the maximum number of arcs in a digraph on $n$ vertices in which there are at most $t$ distinct walks of length $k$ with the same endpoint…

math.CO2021

Extremal digraphs avoiding distinct walks of length 3 with the same endpoints

Zejun Huang, Zhenhua Lyu

In this paper, we determine the maximum size of digraphs on $n$ vertices in which there are no two distinct walks of length $3$ with the same initial vertex and the same terminal v…

math.CO2018

0-1 matrices with zero trace whose squares are 0-1 matrices

Zejun Huang, Zhenhua Lyu

In this paper, we determine the maximum number of nonzero entries in 0-1 matrices of order $n$ with zero trace whose squares are 0-1 matrices when $n \geq 8$ . The extremal matrices a…

math.CO2018

Extremal digraphs avoiding an orientation of $C_{4}$

Zejun Huang, Zhenhua Lyu

Let $P_{2, 2}$ be the orientation of $C_{4}$ which consists of two 2-paths with the same initial and terminal vertices. In this paper, we determine the maximum size of $P_{2, 2}$ -free…

A note on extremal digraphs containing at most t walks of length k with the same endpoints

Extremal digraphs avoiding distinct walks of length 3 with the same endpoints

0-1 matrices with zero trace whose squares are 0-1 matrices

Extremal digraphs avoiding an orientation of C4​

A note on extremal digraphs containing at most $t$ walks of length $k$ with the same endpoints

Extremal digraphs avoiding an orientation of $C_{4}$