广度优先遍历是连通图的一种遍历策略。因为它的思想是从一个顶点V0开始，辐射状地优先遍历其周围较广的区域，故得名。-Breadth first traversal is a kind of traversal strategy of connected graph. Because it s thought is　the beginning of a vertex V0, radiation like to give priority to traverse the wider region, so named.