75. Sort Colors

class Solution 
{
public:
    void sortColors(vector<int>& nums) 
    {
        int pos=0;
        int end=nums.size()-1;
        int num=end;
        int temp;
        if(end==0)//no need to sort
            return;
        bool flag = true;//should continue or not
        while(true)
        {
            while((pos<=num)&&(nums[pos]==0)&&(pos<end))//when red,continue
                ++pos;
            if(pos==end)
                break;//all read have sorted
            while((end>=0)&&(nums[end]!=0)&&(pos<end))//when not red ,continue
                --end;
            if(pos==end)
                break;
            nums[end]=nums[pos];
            nums[pos]=0;
            ++pos;
            //--end;
        }
        end=num;
        while(true)
        {
            while((pos<=num)&&(nums[pos]==1)&&(pos<end))//when white,continue
                ++pos;
            if(pos==end)
                break;//all read have sorted
            while((end>=0)&&(nums[end]!=1)&&(pos<end))//when not white ,continue
                --end;
            if(pos==end)
                break;
            nums[end]=nums[pos];
            nums[pos]=1;
            ++pos;
            //--end;
        }
        
    }
};