View Compilation Error

0_0_16210023_32179.cpp: In function 'int main()':
0_0_16210023_32179.cpp:16:20: error: 'strlen' was not declared in this scope
   int len1=strlen(s),len2=strlen(t),len3=strlen(st);
                    ^
0_0_16210023_32179.cpp:18:25: error: 'memset' was not declared in this scope
   memset(dp,0,sizeof(dp));
                         ^
0_0_16210023_32179.cpp:22:15: error: 'len3' was not declared in this scope
    for(j=i;j<=len3;j++)
               ^
0_0_16210023_32179.cpp:30:15: error: 'len3' was not declared in this scope
   if(dp[len1][len3])
               ^