开两个vector,分别保存奇数,偶数

class Solution {
public:
    void reOrderArray(vector<int> &array) {
        vector<int> even;
        vector<int> odd;

        int len=array.size();
        if(array.empty())
            cout<<0<<endl;

        for(int i=0;i<len;i++){
            if(array[i] % 2)    odd.push_back(array[i]);

            else even.push_back(array[i]);
        }

        int i=0,len1=odd.size();
        for(;i<len1;i++)   array[i]=odd[i];

        int j=i,k=0,len2=even.size();
        for(j=i;k<len2;k++,j++)  array[j] = even[k];

    }
};

双指针写法

class Solution {
public:
    void reOrderArray(vector<int> &array) {
         int i=0,j= array.size()-1;
         while(i<j){
             while(i<j && array[i]%2)   i++;
             while(i<j && array[j]%2 ==0) j--;
             if(i<j)    swap(array[i], array[j]);
         }
    }
};