剑指 Offer 21. 调整数组顺序使奇数位于偶数前面

https://leetcode.cn/problems/diao-zheng-shu-zu-shun-xu-shi-qi-shu-wei-yu-ou-shu-qian-mian-lcof/

解题思路：双指针法

左指针left从左往右遍历，当遇到一个偶数时停止；右指针left从右往左遍历，当遇到一个奇数时停止；同时交换遇到的奇数和偶数

class Solution {
    
    public int[] exchange(int[] nums) {
    
        int left=0,right=nums.length-1;
        while(left<right){
    
            while(left<right&&nums[left]%2==1){
    
                left++;
            }
            while(left<right&&nums[right]%2==0){
    
                right--;
            }
            swap(nums,left,right);
        }
        return nums;
    }
    public void swap(int[] nums,int i,int j){
    
        int tmp=nums[i];
        nums[i]=nums[j];
        nums[j]=tmp;
    }
}
//O(n)
//O(1)

class Solution {
    
public:
    vector<int> exchange(vector<int>& nums) {
    
        int l=0,r=nums.size()-1;
        while(l<r){
    
            while(l<r&&nums[l]%2==1){
    
                l++;
            }
            while(l<r&&nums[r]%2==0){
    
                r--;
            }
            swap(nums[l],nums[r]);
        }
        return nums;

    }
};

class Solution:
    def exchange(self, nums: List[int]) -> List[int]:
        left,right=0,len(nums)-1
        while left < right:
            while left<right and nums[left]%2==1:
                left+=1
            while left<right and nums[right]%2==0:
                right-=1
            nums[left],nums[right]=nums[right],nums[left]
        return nums