Essential C++

includes()

includes() returns true if every element of the second sequence is contained within the first sequence; otherwise, it returns false. Both sequences must be sorted, either by the default less-than operator or by the same operation passed as an optional fifth parameter.

#include <algorithm> 
   int ia1[] = { 13, 1, 21, 2, 0, 34, 5, 1, 8, 3, 21, 34 }; 
int ia2[] = { 21, 2, 8, 3, 5, 1 }; 

// includes must be passed sorted containers 
sort( ia1, ia1+12 ); sort( ia2, ia2+6 ); 
res = includes( ia1, ia1+12, ia2, ia2+6 ); // true