C++ Why is my comparison between int and str.length() not working?

The issue is with the data type names[i].length() returns an unsigned int. Comparing -1 with names[i].length() will always give you a false.

int findLongestName(string names[], int numNames) {
    unsigned int longest = 0;

    for (int i = 0; i < numNames; i++) {
        if (names[i].length() > longest) {
            longest = names[i].length();
        }
    }

    return longest;
}

when comparing a signed value longest with unsigned value names[i].length(), the compiler converts the signed value into an unsigned value, which makes int longest which is initially -1, a very big unsigned number 4294967295

So, essentially, this always evaluates to false:

if (names[i].length() > longest)

Fixes:

You can typecast the unsigned int returned from string.length() into int

if ((int)names[i].length() > longest) {

or make longest an unsigned int from the start