【题目】

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

【分析】

类似于剑指Offer之和为S的两个数字

【代码】

/*********************************
*   日期：2015-01-15
*   作者：SJF0115
*   题目: 1.Two Sum
*   网址：https://oj.leetcode.com/problems/two-sum/
*   结果：AC
*   来源：LeetCode
*   博客：
**********************************/
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

class Solution {
public:
    vector<int> twoSum(vector<int> &numbers, int target) {
        vector<int> result;
        vector<int> num = numbers;
        int count = numbers.size();
        if(numbers.empty()){
            return result;
        }//if
        // 排序
        sort(numbers.begin(),numbers.end());
        // 二分查找变形
        for(int i = 0,j = count-1;i < j;){
            int sum = numbers[i] + numbers[j];
            // 找到目标
            if(sum == target){
                return FindIndex(num,numbers[i],numbers[j]);
            }
            // 当前和大于目标,需要变小一些
            else if(sum > target){
                j--;
            }
            // 当前和小于目标,需要变大一些
            else{
                i++;
            }
        }//for
        return result;
    }
private:
    // 寻找下标
    vector<int> FindIndex(vector<int> &numbers,int num1,int num2){
        int count = numbers.size();
        vector<int> result;
        int index1,index2;
        bool flag1 = false,flag2 = false;
        for(int i = 0;i < count;++i){
            if(flag1 == false && numbers[i] == num1){
                index1 = i+1;
                flag1 = true;
            }
            else if(flag2 == false && numbers[i] == num2){
                index2 = i+1;
                flag2 = true;
            }
        }//for
        // 交换 使index1 < index2
        if(index1 > index2){
            int tmp = index1;
            index1 = index2;
            index2 = tmp;
        }//if
        result.push_back(index1);
        result.push_back(index2);
        return result;
    }
};

int main(){
    Solution solution;
    vector<int> num;
    num.push_back(0);
    num.push_back(4);
    num.push_back(3);
    num.push_back(0);
    //num.push_back(15);
    int target = 0;
    // 查找
    vector<int> vec = solution.twoSum(num,target);
    // 输出
    cout<<"Index1->"<<vec[0]<<" Index2->"<<vec[1]<<endl;
    return 0;
}

[LeetCode]1.Two Sum