View Compilation Error

0_0_36524968_16633.cpp: In function 'int kmp(char*, int, char*, int)':
0_0_36524968_16633.cpp:10:15: error: 'next' was not declared in this scope
     R int i=1;next[1]=0;
               ^
0_0_36524968_16633.cpp: In function 'int main()':
0_0_36524968_16633.cpp:42:19: error: 'strlen' was not declared in this scope
     kmp(a,strlen(a),b,strlen(b));
                   ^