Intel Corporation Interview Question

Given a string, delimited by ';' where each sub string contains a key and value, how would you create a function to allow a user to quickly search the string for a specific value given a key? E.x.: key1=val1;key2=val2;key3=val3 Given input key1 should return val1 and nothing else. Follow up was can you do this without 'strtok()' ?