scholarly journals On Rainbow Connection

10.37236/781 ◽  
2008 ◽  
Vol 15 (1) ◽  
Author(s):  
Yair Caro ◽  
Arie Lev ◽  
Yehuda Roditty ◽  
Zsolt Tuza ◽  
Raphael Yuster

An edge-colored graph $G$ is rainbow connected if any two vertices are connected by a path whose edges have distinct colors. The rainbow connection number of a connected graph $G$, denoted $rc(G)$, is the smallest number of colors that are needed in order to make $G$ rainbow connected. In this paper we prove several non-trivial upper bounds for $rc(G)$, as well as determine sufficient conditions that guarantee $rc(G)=2$. Among our results we prove that if $G$ is a connected graph with $n$ vertices and with minimum degree $3$ then $rc(G) < 5n/6$, and if the minimum degree is $\delta$ then $rc(G) \le {\ln \delta\over\delta}n(1+o_\delta(1))$. We also determine the threshold function for a random graph to have $rc(G)=2$ and make several conjectures concerning the computational complexity of rainbow connection.

2014 ◽  
Vol Vol. 16 no. 3 (Graph Theory) ◽  
Author(s):  
Xiaolong Huang ◽  
Hengzhe Li ◽  
Xueliang Li ◽  
Yuefang Sun

Graph Theory International audience The oriented diameter of a bridgeless graph G is min diam(H) | H is a strang orientation of G. A path in an edge-colored graph G, where adjacent edges may have the same color, is called rainbow if no two edges of the path are colored the same. The rainbow connection number rc(G) of G is the smallest integer number k for which there exists a k-edge-coloring of G such that every two distinct vertices of G are connected by a rainbow path. In this paper, we obtain upper bounds for the oriented diameter and the rainbow connection number of a graph in terms of rad(G) and η(G), where rad(G) is the radius of G and η(G) is the smallest integer number such that every edge of G is contained in a cycle of length at most η(G). We also obtain constant bounds of the oriented diameter and the rainbow connection number for a (bipartite) graph G in terms of the minimum degree of G.


2021 ◽  
Vol 66 (3) ◽  
pp. 3-7
Author(s):  
Anh Nguyen Thi Thuy ◽  
Duyen Le Thi

Let l ≥ 1, k ≥ 1 be two integers. Given an edge-coloured connected graph G. A path P in the graph G is called l-rainbow path if each subpath of length at most l + 1 is rainbow. The graph G is called (k, l)-rainbow connected if any two vertices in G are connected by at least k pairwise internally vertex-disjoint l-rainbow paths. The smallest number of colours needed in order to make G (k, l)-rainbow connected is called the (k, l)-rainbow connection number of G and denoted by rck,l(G). In this paper, we first focus to improve the upper bound of the (1, l)-rainbow connection number depending on the size of connected graphs. Using this result, we characterize all connected graphs having the large (1, 2)-rainbow connection number. Moreover, we also determine the (1, l)-rainbow connection number in a connected graph G containing a sequence of cut-edges.


2019 ◽  
Vol 19 (02) ◽  
pp. 1950001
Author(s):  
YINGYING ZHANG ◽  
XIAOYU ZHU

A path in a vertex-colored graph is a vertex-proper path if any two internal adjacent vertices differ in color. A vertex-colored graph is proper vertex k-connected if any two vertices of the graph are connected by k disjoint vertex-proper paths of the graph. For a k-connected graph G, the proper vertex k-connection number of G, denoted by pvck(G), is defined as the smallest number of colors required to make G proper vertex k-connected. A vertex-colored graph is strong proper vertex-connected, if for any two vertices u, v of the graph, there exists a vertex-proper u-v geodesic. For a connected graph G, the strong proper vertex-connection number of G, denoted by spvc(G), is the smallest number of colors required to make G strong proper vertex-connected. In this paper, we study the proper vertex k-connection number and the strong proper vertex-connection number on the join of two graphs, the Cartesian, lexicographic, strong and direct product, and present exact values or upper bounds for these operations of graphs. Then we apply these results to some instances of Cartesian and lexicographic product networks.


2013 ◽  
Vol 2 (1) ◽  
pp. 78
Author(s):  
Sally Marhelina

An edge-colored graph G is rainbow connected if any two vertices are connected by a path whose edges have distinct colors. The rainbow connection number of aconnected graph G, denoted by rc(G) is the smallest number of colors needed such thatG is rainbow connected. In this paper, we will proved again that rc(G) ≤ 3(n + 1)/5 forall 3-connected graphs, and rc(G) ≤ 2n/3 for all 2-connected graphs.


10.37236/1172 ◽  
2012 ◽  
Vol 19 (1) ◽  
Author(s):  
Xueliang Li ◽  
Sujuan Liu ◽  
L. Sunil Chandran ◽  
Rogers Mathew ◽  
Deepak Rajendraprasad

The rainbow connection number, $rc(G)$, of a connected graph $G$ is the minimum number of colors needed to color its edges, so that every pair of vertices is connected by at least one path in which no two edges are colored the same. Our main result is that $rc(G)\leq \lceil\frac{n}{2}\rceil$ for any 2-connected graph with at least three vertices. We conjecture that $rc(G)\leq n/\kappa+C$ for a $\kappa$-connected graph $G$ of order $n$, where $C$ is a constant, and prove the conjecture for certain classes of graphs. We also prove that $rc(G)\leq(2+\varepsilon)n/\kappa+23/\varepsilon^2$ for any $\varepsilon>0$.


2020 ◽  
Vol 3 (2) ◽  
pp. 95
Author(s):  
Alfi Maulani ◽  
Soya Pradini ◽  
Dian Setyorini ◽  
Kiki A. Sugeng

Let <em>G </em>= (<em>V</em>(<em>G</em>),<em>E</em>(<em>G</em>)) be a nontrivial connected graph. A rainbow path is a path which is each edge colored with different color. A rainbow coloring is a coloring which any two vertices should be joined by at least one rainbow path. For two different vertices, <em>u,v</em> in <em>G</em>, a geodesic path of <em>u-v</em> is the shortest rainbow path of <em>u-v</em>. A strong rainbow coloring is a coloring which any two vertices joined by at least one rainbow geodesic. A rainbow connection number of a graph, denoted by <em>rc</em>(<em>G</em>), is the smallest number of color required for graph <em>G</em> to be said as rainbow connected. The strong rainbow color number, denoted by <em>src</em>(<em>G</em>), is the least number of color which is needed to color every geodesic path in the graph <em>G</em> to be rainbow. In this paper, we will determine  the rainbow connection and strong rainbow connection for Corona Graph <em>Cm</em> o <em>Pn</em>, and <em>Cm</em> o <em>Cn</em>.


Author(s):  
Rizki Hafri Yandera ◽  
Yanne Irene ◽  
Wisnu Aribowo

AbstractLet  be a nontrivial connected graph, the rainbow-k-coloring of graph G is the mapping of c: E(G)-> {1,2,3,…,k} such that any two vertices from the graph can be connected by a rainbow path (the path with all edges of different colors). The least natural number


2019 ◽  
Vol 8 (1) ◽  
pp. 345
Author(s):  
Risya Hazani Utari ◽  
Lyra Yulianti ◽  
Syafrizal Sy

Suatu pewarnaan terhadap sisi-sisi di graf G terhubung tak trivial didefinisikan sebagai c : E(G) → {1, 2, · · · , k} untuk k ∈ N adalah suatu pewarnaan terhadap sisi-sisi di G sedemikian sehingga setiap sisi yang bertetangga boleh diberi warna yang sama. Banyaknya warna minimal yang diperlukan untuk membuat graf G bersifat rainbow connected disebut dengan rainbow connection number dari G, yang dinotasikan dengan rc(G). Penelitian ini menentukan rainbow connection number untuk amalgamasi 2 buah graf lengkap K4 dengan 2 buah graf roda W4 yang diperoleh dari menggabungkan satu titik pada setiap graf lengkap K4 dengan satu titik pusat pada setiap graf roda W4.Kata Kunci: Amalgamasi, Graf lengkap K4, Graf Roda W4, Rainbow Connection Number


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