703186. Pair the minimum
Pair the Minimum5535
Summary
The problem "Pair the minimum" is about given an array of integers and a target sum, find all pairs that add up to the target sum. This problem involves working with arrays and data structures, specifically finding a specific pattern within the array.
Detailed Explanation
To solve this problem, we can use a simple two-pointer technique. We first sort the array in ascending order. Then, we initialize two pointers, one at the start of the array (let's call it left) and one at the end of the array (right). We calculate the sum of the elements at these positions.
If the sum is less than the target sum, we move the left pointer to the right to increase the sum. If the sum is greater than the target sum, we move the right pointer to the left to decrease the sum. When the sum equals the target sum, we have found a pair that adds up to the target sum.
We keep track of all these pairs and return them as the result. This solution has a time complexity of O(n log n) due to the sorting step, where n is the size of the array. The space complexity is O(n) for storing the result.
Here's a step-by-step breakdown of the solution:
- Sort the input array in ascending order.
- Initialize two pointers,
leftandright, at the start and end of the array respectively. - Calculate the sum of the elements at the positions pointed by
leftandright. - If the sum is less than the target sum, move the
leftpointer to the right to increase the sum. - If the sum is greater than the target sum, move the
rightpointer to the left to decrease the sum. - When the sum equals the target sum, add the pair to the result and move both pointers towards each other.
- Repeat steps 3-6 until the
leftandrightpointers meet or cross over. - Return the list of pairs that add up to the target sum.
Optimized Solutions
Java
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class PairTheMinimum {
public static List<List<Integer>> pairTheMinimum(int[] arr, int target) {
Arrays.sort(arr);
List<List<Integer>> result = new ArrayList<>();
int left = 0, right = arr.length - 1;
while (left < right) {
int sum = arr[left] + arr[right];
if (sum == target) {
result.add(Arrays.asList(arr[left], arr[right]));
left++;
right--;
} else if (sum < target) {
left++;
} else {
right--;
}
}
return result;
}