题解 | #三数之和#C++暴力排序解法

class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param num int整型vector 
     * @return int整型vector<vector<>>
     */
    vector<vector<int> > threeSum(vector<int>& num) 
    {
        int i=0;
        int j=0;
        int len=num.size();
        unordered_map<int,int> hash;
        sort(num.begin(),num.end());
        for(i=0;i<len;i++)
        {
            if(hash.count(num[i])==0)
            {
                hash[num[i]]=1;
            }
            else 
            {
                hash[num[i]]++;
            }
        }
        vector <vector <int>> ans;
        for(i=0;i<len-2;i++)
        {
            for(j=i+1;j<len-1;j++)
            {
                int m=num[i]+num[j];
                m=0-m;
                if(m==num[i]  &&  m==num[j])
                {
                    if(hash[m]>=3)
                    {
                        vector <int> b;
                        b.push_back(m);
                        b.push_back(m);
                        b.push_back(m);
                        ans.push_back(b);
                    }
                }
                else 
                {
                    if(m==num[i])
                    {
                        if(hash[m]>=2)
                        {
                            vector <int> b;
                            b.push_back(m);
                            b.push_back(m);
                            b.push_back(num[j]);
                            sort(b.begin(),b.end());
                            ans.push_back(b);
                        }
                    }
                    else 
                    {
                        if(m==num[j])
                        {
                            if(hash[m]>=2)
                            {
                                vector <int> b;
                                b.push_back(m);
                                b.push_back(m);
                                b.push_back(num[i]);
                                sort(b.begin(),b.end());
                                ans.push_back(b);
                            }
                        }
                        else 
                        {
                            if(hash.count(m))
                            {
                                vector <int> b;
                                b.push_back(m);
                                b.push_back(num[j]);
                                b.push_back(num[i]);
                                sort(b.begin(),b.end());
                                ans.push_back(b);
                            }
                        }
                    }
                }
            }
        }
        sort(ans.begin(),ans.end());
        ans.erase(unique(ans.begin(),ans.end()),ans.end());
        return ans;
    }
};