Welcome to Programming and Data Structures

Strings support some of the same operators as numbers. For example, we can use the comparison operators to compare strings:

The equality tests are straightforward. "apple" is the same as itself, but not the same as "Banana". Looking at the comparison between "apple" and "Apple", it is clear that comparisons are case sensitive—they care about the difference between a and A.

The “less than” tests are a little less obvious. But they make sense when you recall that characters have numeric values based on their position in the ASCII table (or Unicode table for wide characters). Why is "Apple" less than "Banana"? Because A comes before B on the ASCII table. Why is "Banana" less than "apple"? Because B comes before a on the ASCII table. If the first n characters of two strings match, the n + 1 characters will determine their order "pear" < "peer" is true because both start with pe and the third character in pear - a - is less than the 3rd character in peer - e`.

Strings also support the + operator. But for strings + does not mean “plus”. It means concatenate, which is a fancy way of saying “join end-to-end”. So "Hello, " + "World!" yields the string "Hello, World!".

+ and the += shortcut is useful if you want to build up a string piece by piece.

string name = "Ada";
name = name + " Lovelace"; // name is now "Ada Lovelace"
string greeting = "Hello, " + name + "!";
                           // greeting is now "Hello, Ada Lovelace!"

string name2 = "Alan";
name2 += " Turing";        // name2 is now "Alan Turing"

Many string algorithms involve reading one string and building another. For example, to reverse a string, we can concatenate one character at a time to the front of a new string. The initial value of reversed is "", which is an empty string. As we iterate through each character, we set reversed to be that character concatenated with the other characters we have seen. Since the loop goes from beginning to end, adding each character to the front of reversed means that the last character of myString ends up being the first character of reversed:

"bread" < "bread";

"car" == "Car";

"Dog" < "Doghouse";

"dog" < "Dog";