C++ Programming- Please help

// "How much wood could a woodchuck chuck" contains 11 vowels. How do we // know? Five of the 26 English alphabet letters are vowels: a, e, i, o, // and u. By looking at each letter in the woodchuck string, we find // 11 vowels. Complete function vowelCount that returns the number of vowels // in the given std::string argument. This is case insensitive. Upper and lower // case vowels count. We do not consider y to be a vowel. // // vowelCount("a e i o u A E I O U") returns 10 // vowelCount("y+_x1Y2x!y") returns 0 // int vowelCount(std::string str) { // TODO: Complete this function return -999; }