Two Sum

Given an array of integers, find two numbers such that they add up to a specific target number.

The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2. Please note that your returned answers (both index1 and index2) are not zero-based.

You may assume that each input would have exactly one solution.

Input: numbers={2, 7, 11, 15}, target=9
Output: index1=1, index2=2

1.自己写的快排，Time limited

#include<iostream>#include<vector>#include<map>using namespace std;class Solution {public:    vector<int> twoSum(vector<int> &numbers, int target) {//check……//建立映射int nSize = numbers.size();map<int,int> num;for(int i = 0;i != nSize;i ++){num.insert(pair<int, int>(numbers[i],i+1));}//对元素数据进行快排m_QickSort(numbers,0,nSize-1);//searchint k = 0,j = nSize - 1;while (k < j ){int sum = numbers[k] + numbers[j];if(sum == target)break;else if(sum < target)k++;elsej--;}vector<int> result;result.push_back(num[numbers[k]]);result.push_back(num[numbers[j]]);return result;    }void m_QickSort(vector<int> &numbers, int nStart, int nEnd){//check……if(nStart == nEnd)return;else{int nMid = m_Partition(numbers,nStart,nEnd);if(nMid > nStart)m_QickSort(numbers,nStart,nMid - 1);if(nMid < nStart)m_QickSort(numbers,nMid + 1,nEnd);}}int m_Partition(vector<int> &numbers,int nStart,int nEnd){//check……if( nStart >= nEnd )return nStart;else{int nCompare = numbers[nEnd];int nTemp , j = nStart;for( int i = nStart; i < nEnd; i ++){if( numbers[i] < nCompare){nTemp = numbers[j];numbers[j] = numbers[i];numbers[i] = nTemp;j++;}}nTemp = numbers[j];numbers[j] = numbers[nEnd];numbers[nEnd] = nTemp;return j;}}};int main(){Solution solution;int a[] = {3, 2, 4};vector<int> Test(a, a + sizeof(a)/sizeof(int));vector<int> Result;Result = solution.twoSum(Test,6);cout<<Result[0]<<endl<<Result[1];getchar();return 0;}

2.采用STL中排序函数 accepted:

#include<iostream>#include<vector>#include<map>#include<algorithm>using namespace std;class Solution {public:    vector<int> twoSum(vector<int> &numbers, int target) {//check……int nSize = numbers.size();vector<int> orignal = numbers;sort(numbers.begin(),numbers.end());//searchint k = 0,j = nSize - 1;int sum;while (k < j ){sum = numbers[k] + numbers[j];if(sum == target)break;else if(sum < target)k++;elsej--;}vector<int> result;vector<int>::iterator First = find(orignal.begin(),orignal.end(),numbers[k]);vector<int>::iterator Second = find(orignal.begin(),orignal.end(),numbers[j]);if(First == Second)Second = find(First + 1,orignal.end(),numbers[j]);int a = First - orignal.begin() + 1;int b = Second - orignal.begin() + 1;result.push_back( (a<b)?a:b );result.push_back( (a>b)?a:b);return result;    }};int main(){Solution solution;int a[] = {0,4,3,0};vector<int> Test(a, a + sizeof(a)/sizeof(int));vector<int> Result;Result = solution.twoSum(Test,0);cout<<Result[0]<<endl<<Result[1];getchar();return 0;}