3. The method of claim 1 , wherein determining the searching cost associated with the navigation hierarchical structure diagram includes: calculating a viewing cost of the navigation hierarchical structure diagram based at least in part on confidence levels of leaf nodes associated with the navigation hierarchical structure diagram and branch positions corresponding to the leaf nodes; calculating a clicking cost of the navigation hierarchical structure diagram based at least in part on confidence levels of the leaf nodes and hierarchical positions corresponding to the leaf nodes; and calculating the searching cost associated with the navigation hierarchical structure diagram based at least in part on the clicking cost and the viewing cost.
3. The method of claim 1 , wherein determining the searching cost associated with the navigation hierarchical structure diagram includes: calculating a viewing cost of the navigation hierarchical structure diagram based at least in part on confidence levels of leaf nodes associated with the navigation hierarchical structure diagram and branch positions corresponding to the leaf nodes; calculating a clicking cost of the navigation hierarchical structure diagram based at least in part on confidence levels of the leaf nodes and hierarchical positions corresponding to the leaf nodes; and calculating the searching cost associated with the navigation hierarchical structure diagram based at least in part on the clicking cost and the viewing cost. 7. The method of claim 3 , wherein calculating the viewing cost v_cost ij of the navigation hierarchical structure diagram includes using: v_cost ij = v_cost ⁢ ( query i , tr j ) = ∑ k = 1 K ⁢ ⁢ v k * h ⁡ ( query i , v_cat k ) wherein: query i , represents search request i; tr j represents the jth navigation hierarchical structure diagram; v_cat k represents the Level 1 kth position node of the jth navigation hierarchical structure diagram; v k represents the viewing cost of v_cat k ; h(query i ,v_cat k ) represents the confidence level for node v_cat k , h(query i ,v_cat k ) represents the sum of the confidence levels for all of the child and grandchild leaf nodes; and K is the total number of leaf nodes in the jth navigation hierarchical structure diagram.