独立集是指图 G 中两两互不相邻的顶点构成的集合。任意有关图中团的性质都能很自然的转述成独立集的性质。一般而言，寻找图的最大团是 NP 困难的，从而寻找图的最大独立集也是 NP 困难的。用模拟退火算法找出图的最大独立集。(Independent set is a set of vertices in graph G that are not adjacent to each other. The properties of cliques in any graph can be naturally expressed as the properties of independent sets. Generally speaking, it is NP-hard to find the maximum clique of a graph, so it is NP-hard to find the maximum independent set of a graph. Simulated annealing algorithm is used to find the maximum independent set of graphs.)