View Compilation Error

0_0_19877977_20797.cpp: In function 'void build(int, int, int)':
0_0_19877977_20797.cpp:24:20: error: return-statement with a value, in function returning 'void' [-fpermissive]
             return 0;//如果当前节点的l==r，那么这个就是叶子节点，不需要构建其左右孩子
                    ^