A cluster graph is an undirected graph composed of disjoint maximal cliques. In this thesis, we study the problem Min-Max Cluster Editing which minimizes the maximum number of inserting and deleting edges incident to any vertex. We design a 2-approximation algorithm and show a polynomial-time solvable case. We also present a branching algorithm for solving the problem exactly. Another problem is a variant of p-Correlation Clustering named p-Correlation Clustering for Labelled Items (p-CCLI). For this problem, each vertex is given one or more label indicating the cluster it can be clustered into. For p-CCLI, we design some reduction rules and present a tree-search algorithm. By experiments on random graphs, we show the performance of our algorithms.