输入一个简单（无多重边和自环）的连通无向图，判断该图是否能用黑白两种颜色对顶点染色，使得每条边的两个端点为不同颜色。-Enter a simple (no multiple edges and loopback) connectivity undirected graph, determine if you can use this figure in black or white stained pair of vertices, so that the two ends of each si