View Compilation Error

0_0_30099558_8521.cpp: In function 'void update(int, int, int, int, int)':
0_0_30099558_8521.cpp:33:9: error: 'a' was not declared in this scope
         a[k] =v ;t[k] = v;  }  //原数组和线段树数组都得到更新
         ^
0_0_30099558_8521.cpp: In function 'int main()':
0_0_30099558_8521.cpp:86:10: error: 'a' was not declared in this scope
   memset(a,0,sizeof(a));
          ^