1.两数之和

 1 class Solution {
 2 public:
 3     vector<int> twoSum(vector<int>& nums, int target) {
 4         vector<int>result;
 5         for(int i=0;i<nums.size();i++)
 6             for(int j=i+1;j<nums.size();j++)
 7                 if(nums[i]+nums[j]==target){
 8                     result.push_back(i);
 9                     result.push_back(j);
10                     return result;
11                 }
12         return result;
13     }  
14 };

 1 class Solution {
 2 public:
 3     vector<int> twoSum(vector<int>& nums, int target) {
 4         vector<int>result;
 5         map<int,int>tmpmap;
 6         for(int i=0;i<nums.size();i++)
 7             tmpmap[nums[i]]=i;
 8         for(int i=0;i<nums.size();i++){
 9             if(tmpmap.count(target-nums[i])!=0&&tmpmap[target-nums[i]]!=i){
10                 result.push_back(i);
11                 result.push_back(tmpmap[target-nums[i]]);
12                 break;
13             }
14         }
15         return result;
16     }  
17 };