Interleaving Positive and Negative Numbers

最新推荐文章于 2020-08-21 12:08:29 发布

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本文介绍了一种算法，该算法接收一个包含正负整数的数组，并将其重新排列为正负整数交错的形式。无需保持原始顺序，通过排序及交换操作实现目标排列。

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Given an array with positive and negative integers. Re-range it to interleaving with positive and negative integers.

Notice

You are not necessary to keep the original order of positive integers or negative integers.

Have you met this question in a real interview?

Yes

Example

Given [-1, -2, -3, 4, 5, 6], after re-range, it will be [-1, 5, -2, 4, -3, 6] or any other reasonable answer.

一个写的并不简洁的代码

java

public class Solution {
    /*
     * @param A: An integer array.
     * @return: nothing
     */
    public void rerange(int[] nums) {
        // write your code here
        if (nums == null || nums.length < 3) {
            return;
        }
        Arrays.sort(nums);
        int size = nums.length;
        boolean flag = true;
        int left = 0;
        int right = 0;
        if (size % 2 == 0) {
            left = 0;
            right = size - 1;
            while (left <= right) {
                if (flag && left <= right) {
                    left++;
                    right--;
                    flag = !flag;
                } else if (!flag && left <= right){
                    reverse(nums, left, right);
                    left++;
                    right--;
                    flag = !flag;
                }
            }
        }
        
        else if (size % 2 == 1 && nums[nums.length / 2] < 0) {
            left = 1;
            right = size - 1;
            while (left <= right) {
                if (flag && left <= right) {
                    reverse(nums, left, right);
                    left++;
                    right--;
                    flag = !flag;
                } else if (!flag && left <= right) {
                    left++;
                    right--;
                    flag = !flag;
                }
            }
        }
        
        else if (size % 2 == 1 && nums[nums.length / 2] > 0) {
            left = 0;
            right = size - 2;
            while (left <= right) {
                if (flag && left <= right) {
                    reverse(nums, left, right);
                    left++;
                    right--;
                    flag = !flag;
                } else if (!flag && left <= right) {
                    left++;
                    right--;
                    flag = !flag;
                }
            }
        }
    }
    
    private void reverse(int[] nums, int start, int end) {
        int temp = nums[start];
        nums[start] = nums[end];
        nums[end] = temp;
    }
}

简化后的代码

java

public class Solution {
    /*
     * @param A: An integer array.
     * @return: nothing
     */
    public void rerange(int[] nums) {
        // write your code here
        if (nums == null || nums.length < 3) {
            return;
        }
        int left = 0;
        int right = 0;
        boolean flag = true;
        Arrays.sort(nums);
        if (nums.length % 2 == 0) {
            left = 0;
            right = nums.length - 1;
            flag = true;
        } else if (nums.length % 2 == 1 && nums[nums.length / 2] < 0) {
            left = 1;
            right = nums.length - 1;
            flag = false;
        } else if (nums.length % 2 == 1 && nums[nums.length / 2] > 0) {
            left = 0;
            right = nums.length - 2;
            flag = false;
        } else {
            return;
        }
        while (left <= right) {
            if (left <= right && flag) {
                left++;
                right--;
                flag = !flag;
            } else if (left <= right && !flag) {
                reverse(nums, left, right);
                left++;
                right--;
                flag = !flag;
            }
        }
    }
    
    private void reverse(int[] nums, int left, int right) {
        int temp = nums[left];
        nums[left] = nums[right];
        nums[right] = temp;
    }
}

python

class Solution:
    """
    @param: A: An integer array.
    @return: nothing
    """
    def rerange(self, nums):
        # write your code here
        if nums is None or len(nums) < 3:
            return
        left, right, flag = 0, 0, True
        nums.sort()
        if len(nums) % 2 == 0:
            left, right, flag = 0, len(nums) - 1, True
        elif len(nums) % 2 == 1 and nums[len(nums) / 2] < 0:
            left, right, flag = 1, len(nums) - 1, False
        elif len(nums) % 2 == 1 and nums[len(nums) / 2] > 0:
            left, right, flag = 0, len(nums) - 2, False
        else:
            return 
        while left <= right:
            if left <= right and flag:
                left += 1
                right -= 1
                flag = not flag
            elif left <= right and not flag:
                nums[left], nums[right] = nums[right], nums[left]
                left += 1
                right -= 1
                flag = not flag