View Compilation Error

0_0_20985249_20535.cpp: In function 'void BFS()':
0_0_20985249_20535.cpp:22:27: error: 'memset' was not declared in this scope
 memset(mark,0,sizeof(mark));
                           ^
0_0_20985249_20535.cpp: In function 'int main()':
0_0_20985249_20535.cpp:94:23: error: 'memset' was not declared in this scope
 memset(a,'*',sizeof(a));
                       ^