void  BuildTableStr(Node * root){


          if (root->left!=NULL){
                shCode.push_back("0");
                BuildTableStr(root->left);
                  }
          if (root->right!=NULL){
                      shCode.push_back("1");
                      BuildTableStr(root->right);
                  }
          if(root->left==NULL && root->right == NULL) strTable[root->ch] = shCode;

          if (shCode.size () > 0)  shCode.resize (shCode.size () - 1);
              }