probem:1. Two Sum

 今天先熟悉熟悉， 希望后面能一次就过
 1 #include <vector>
#include <algorithm>

using namespace std;

bool mycompare(const pair<int, int>&a, const pair<int, int>& b)
{
    return a.first < b.first;
}

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        vector<pair<int, int> > vecPair(nums.size());
        for (size_t i = 0; i < vecPair.size(); ++i){
            vecPair[i] = make_pair(nums[i], i);
        }
        sort (vecPair.begin(), vecPair.end(), mycompare);
        vector<int> result;
        int a = 0;
        int b = vecPair.size()-1;
        while (a<b){
            int sum = vecPair[a].first + vecPair[b].first;
            if (sum == target){
                break;
            }
            if (sum < target){
                ++ a;
            }
            else {
                -- b;
            }
        }
        if (a < b){
            result.push_back(vecPair[a].second);
            result.push_back(vecPair[b].second);
        }
        return result;
    }
};