I'm doing my homework,that i need to use quick sort to sort string array,and the element in array combing number and string. for example
String s[];
s[0]="172,19,Nina";
s[1]="178,18,Apple";
s[2]="178,18,Alex";
So after sorted, it should be
s[0]=172,19,Nina
s[1]=178,18,Alex
s[2]=178,18,Apple
Im thinking should i split all the Strings first into number and string, and then sort 172,178,178, and then sort 19 18 18, and at the end sort Nina Apple Alex??
what is the best way to do this?
If all your numbers have the same number of characters, lexicographic order is the same as numeric order, so you might just compare your Strings directly.
Else, you should split the strings and transform them into proper objects which implement the Comparable interface:
public class Record implements Comparable<Record> {
private int firstNumber;
private int secondNumber;
private String name;
...
@Override
public int compareTo(Record r) {
int result = Integer.valueOf(firstNumber).compareTo(Integer.valueOf(r.firstNumber);
if (result != 0) {
result = Integer.valueOf(secondNumber).compareTo(Integer.valueOf(r.secondNumber);
}
if (result != 0) {
result = name.compareTo(r.name);
}
return result;
}
}
Yes, you are right: you need to separate the combined string into its elements and sort the array based on these separated elements. Note that you do not need to sort the full array based on the first number, then the second, etc., but provide a comparison logic based on them. This is called lexical ordering
Basically, when you need to decide whether an element is less then another, you have the following logic (pseudocode):
if elem1's first number < elem2's first number
then
return elem1 less than elem2
else if elem1's first number > elem2's first number
then
return elem1 greater than elem2
// from here on: elem1's first number == elem2's first number
else if elem1's second number < elem2's second number
then
return elem1 less then elem2
else if elem1's second number > elem2's second number
then
return elem1 greater than elem2
// from here on: elem1's second number == elem2's second number
else if elem1's third string < elem2's third string
then
return elem1 less then elem2
else if elem1's third string > elem2's third string
then
return elem1 greater than elem2
else // everything is the same
return elem1 equal elem2
compareTo()method a solution here? Asking this question to people who see this question,not to the OP.