View Compilation Error

0_0_13802577_18748.cpp: In function 'bool fit(char*, char*)':
0_0_13802577_18748.cpp:33:17: error: 'strlen' was not declared in this scope
  if(s1[strlen(s1)-1]==s2[0])
                 ^
0_0_13802577_18748.cpp: In function 'int main()':
0_0_13802577_18748.cpp:105:27: error: 'strcmp' was not declared in this scope
    if(strcmp(str[i],str[j])==0)
                           ^
0_0_13802577_18748.cpp:110:27: error: 'strcmp' was not declared in this scope
    if(strcmp(str[i],str[j])==0)
                           ^
0_0_13802577_18748.cpp:114:20: error: expected ')' before ';' token
   scanf("%d",×);
                    ^
0_0_13802577_18748.cpp:114:21: error: expected primary-expression before ')' token
   scanf("%d",×);
                     ^