C++ :: Comparing Value To Array And Outputting

i have 3 arrays total, 2 of them i am comparing to see if any of the values match at all, and then i am putting the value that matches into the 3rd array. currently i am trying

int isthere (int match[], int maxmatchLength,
const int vec1[], int vec1Length,
const int vec2[], int vec2Length)
{
for (i=0; i<vec1Length; i++)
if vec1[i]==vec2[i];
vec1[i] = match[i];
}

But this will just match the same values are in the same spot. how do i fix it so that it compares one value in the first array to the whole second array, before going to the next number.