two sum

//method 1: quick sort + Loop

//beat 89%

void quickSort(vector<int> &nums,int iLeft,int iRight,int *arrIndex){

    if(iLeft>=iRight)

        return;

    int idxRand = rand()%(iRight-iLeft+1) + iLeft;

    int idxRand_Index = arrIndex[idxRand];

    int iPivot = nums[idxRand];

    

    nums[idxRand] = nums[iLeft];

    arrIndex[idxRand] = arrIndex[iLeft];

    

    int iBegin = iLeft;

    int iEnd = iRight;

    while(iBegin<iEnd){

        while(iBegin<iEnd && nums[iEnd]>=iPivot)

            iEnd--;

        nums[iBegin] = nums[iEnd];

        arrIndex[iBegin] = arrIndex[iEnd];

        

        while(iBegin<iEnd && nums[iBegin]<=iPivot)

            iBegin++;

        nums[iEnd] = nums[iBegin];

        arrIndex[iEnd] = arrIndex[iBegin];

    }

    nums[iBegin] = iPivot;

    arrIndex[iBegin] = idxRand_Index;

    

    quickSort(nums,iLeft,iBegin-1,arrIndex);

    quickSort(nums,iBegin+1,iRight,arrIndex);

}



vector<int> twoSum(vector<int>& nums, int target) {

    vector<int> retArr;

    

    //sort

    int *arrIndex = (int *)malloc(sizeof(int)*nums.size());

    for(int iLoop=0;iLoop<nums.size();iLoop++){

        arrIndex[iLoop]=iLoop;

    }

    quickSort(nums,0,nums.size()-1,arrIndex);

    

    //search

    int iLeft = 0;

    int iRight = nums.size()-1;

    while(iLeft<iRight){

        int sum = nums[iLeft]+nums[iRight];

        if(sum==target)

        {

            retArr.push_back(arrIndex[iLeft]+1);

            retArr.push_back(arrIndex[iRight]+1);

            break;

        }

        else if(sum<target)

            iLeft++;

        else //sum>target

            iRight--;

    }

    

    

    free(arrIndex);

    sort(retArr.begin(),retArr.end());

    return retArr;

}



//method 2: use std::map<int,int>

//beat 25%

vector<int> twoSum1(vector<int>& nums, int target) {

    map<int,int> m;

    vector<int> retVec;

    for(int iLoop = 0;iLoop < nums.size();iLoop++){

        auto itr= m.find(target-nums[iLoop]);

        if(itr==m.end()){

            m[nums[iLoop]] = iLoop;

        }

        else

        {

            retVec.push_back(itr->second+1);

            retVec.push_back(iLoop+1);

            break;

        }

    }

    return retVec;

}