561. Array Partition I(Java)

本文介绍了一道算法题目,任务是将给定的2n个整数分成n组,每组两个整数,使得所有组中小的那个整数之和尽可能大。通过排序和选择每个偶数位置上的元素来解决这个问题。

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Given an array of 2n integers, your task is to group these integers into n pairs of integer, say (a1, b1), (a2, b2), …, (an, bn) which makes sum of min(ai, bi) for all i from 1 to n as large as possible.

Example 1:
Input: [1,4,3,2]

Output: 4
Explanation: n is 2, and the maximum sum of pairs is 4 = min(1, 2) + min(3, 4).
Note:
1、n is a positive integer, which is in the range of [1, 10000].
2、All the integers in the array will be in the range of [-10000, 10000].

public class Solution {
    public int arrayPairSum(int[] nums) {
        Arrays.sort(nums);
        int res = 0;
        for (int i = 0; i < nums.length; i += 2) 
            res += nums[i];
        return res;
    }
}
``` package oy.tol.tra; import java.util.function.Predicate; public class Algorithms { public static <T extends Comparable<T>> void reverse(T[] array) { int i = 0; int j = array.length - 1; while (i < j) { T temp = array[i]; array[i] = array[j]; array[j] = temp; i++; j--; } } public static <T extends Comparable<T>> void sort(T[] array) { boolean swapped; for (int i = 0; i < array.length - 1; i++) { swapped = false; for (int j = 0; j < array.length - 1 - i; j++) { if (array[j].compareTo(array[j + 1]) > 0) { T temp = array[j]; array[j] = array[j + 1]; array[j + 1] = temp; swapped = true; } } if (!swapped) break; } } public static <T extends Comparable<T>> int binarySearch(T aValue, T[] fromArray, int fromIndex, int toIndex) { int low = fromIndex; int high = toIndex ; while (low <= high) { int mid = low + (high - low) / 2; int cmp = fromArray[mid].compareTo(aValue); if (cmp < 0) { low = mid + 1; } else if (cmp > 0) { high = mid - 1; } else { return mid; } } return -1; } public static <E extends Comparable<E>> void fastSort(E[] array) { quickSort(array, 0, array.length - 1); } private static <E extends Comparable<E>> void quickSort(E[] array, int begin, int end) { if (begin < end) { int partitionIndex = partition(array, begin, end); quickSort(array, begin, partitionIndex - 1); quickSort(array, partitionIndex + 1, end); } } public static <T> int partition(T[] array, int count, Predicate<T> rule) { if (array == null || count <= 0) { return 0; // No elements to partition } int left = 0; // Pointer for elements that satisfy the rule int right = count - 1; // Pointer for elements that do not satisfy the rule while (left <= right) { // Move the left pointer to the right until an element does not satisfy the rule while (left <= right && rule.test(array[left])) { left++; } // Move the right pointer to the left until an element satisfies the rule while (left <= right && !rule.test(array[right])) { right--; } // Swap elements if pointers have not crossed if (left <= right) { T temp = array[left]; array[left] = array[right]; array[right] = temp; left++; right--; } } // Return the index of the first element that does not satisfy the rule return left; } }```The method partition(T[], int, Predicate<T>) in the type Algorithms is not applicable for the arguments (E[], int, int)Java(67108979)
最新发布
03-11
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