LintCode 144 [Interleaving Positive and Negative Numbers]

原题

给出一个含有正整数和负整数的数组，重新排列成一个正负数交错的数组。

样例
给出数组[-1, -2, -3, 4, 5, 6]，重新排序之后，变成[-1, 5, -2, 4, -3, 6]
或者其他任何满足要求的答案

解题思路

• 扫第一遍，确定正数多还是负数多，多的放在0位
• partition数组，前面都是正数后面都睡负数，或者相反，根据谁多
• 两步一跳，生成需要的正负间隔的数组

完整代码

class Solution:
    """
    @param A: An integer array.
    @return nothing
    """
    def rerange(self, A):
        # write your code here
        pos, neg = 0, 0
        for num in A:
            if num > 0:
                pos += 1
            else:
                neg += 1
        if pos > neg:
            left, right = 0, len(A) - 1
            while left < right:
                while A[left] > 0 and left < right:
                    left += 1
                while A[right] < 0 and left < right:
                    right -= 1
                if left <= right:
                    A[left], A[right] = A[right], A[left]
                    left += 1
                    right -= 1
            left, right = 1, len(A) - 1
            while left < right:
                A[left], A[right] = A[right], A[left]
                left += 2
                right -= 2
        else:
            left, right = 0, len(A) - 1
            while left < right:
                while A[left] < 0 and left < right:
                    left += 1
                while A[right] > 0 and left < right:
                    right -= 1
                if left <= right:
                    A[left], A[right] = A[right], A[left]
                    left += 1
                    right -= 1
            if pos == neg:
                left, right = 1, len(A) - 2
            else:
                left, right = 1, len(A) - 1
            while left < right:
                A[left], A[right] = A[right], A[left]
                left += 2
                right -= 2