66 lines
1.8 KiB
Text
66 lines
1.8 KiB
Text
---
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id: pairs-tuples
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title: Pairs & Tuples
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author: Aaron Chew, Benjamin Qi, Nathan Wang, Darren Yao
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description: Introduces pairs, which allow you to store two objects (possibly of different types) as a single unit, as well as tuples, which are a generalization of pairs.
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frequency: 0
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---
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(never needed but uh it's pretty useful lol)
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## Pairs
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## C++
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### [Pair](http://www.cplusplus.com/reference/utility/pair/pair/)
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- `make_pair(a, b)`: Returns a pair with values a, b.
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- `pair.first`: The first value of the pair.
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- `pair.second`: The second value of the pair.
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Of course, we can hold more than two values with something like `pair<int,pair<int,int>>`.
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Example:
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```cpp
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#include <iostream>
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using namespace std;
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int main() {
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pair<string, int> myPair = make_pair("Testing", 123);
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cout << myPair.first << " " << myPair.second << endl; // Testing 123
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}
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/* Output
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* Testing 123
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*/
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```
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### Tuple
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(anyone use?)
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## Java
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Unfortunately there is no default class for pairs in java, so you have to create your own.
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```java
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class pair implements Comparable <pair>{
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int first;
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int second;
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public int compareTo(pair other) {
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return first==other.first?second-other.second:first-other.first;
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}
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pair(int a, int b) {
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first=a;
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second=b;
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}
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}
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```
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If you have an array ```pair[]arr=new pair[100]```, make sure each element of this array is not null. You can call ```Arrays.sort(arr);``` on this array and it will sort it by all the ```first``` of the array and if there is a tie in ```first``` it will sort by ```second```.
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You can also use an `int[]` as a pair, or if you're using a pair of two different types, you can use `Object[]`.
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If you want to sort by 3 or more elements, it's a simple change. Just add a new variable in ```pair``` and make sure the comparable compares in the right order you want.
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