View Compilation Error

0_0_22723196_28201.cpp: In function 'void update(int, int, int)':
0_0_22723196_28201.cpp:46:5: error: 'a' was not declared in this scope
     a[x] = val;
     ^
0_0_22723196_28201.cpp:49:9: error: 'maxVal' was not declared in this scope
         maxVal[i] = a[i];
         ^
0_0_22723196_28201.cpp:52:53: error: 'max' was not declared in this scope
             maxVal[i] = max(maxVal[i], maxVal[i - j]);
                                                     ^
0_0_22723196_28201.cpp: In function 'int main()':
0_0_22723196_28201.cpp:82:28: error: too few arguments to function 'void update(int, int, int)'
             else update(a,b);  
                            ^
0_0_22723196_28201.cpp:44:6: note: declared here
 void update(int x, int val, int n) // 单单改变父亲结点是不够的，因为无法确定这段区间中的最大值来自哪里，
      ^