0001_two_sum

说明：

这里有一个坑，题目中容易误解为不存在相同的元素。这里如果数组中存在相同的元素也是可以的。

class Solution {
public:
    vector<int> twoSum(vector<int>& nums, int target) {
        map<int, vector<int>> m;
        vector<int> res;
        for (int i = 0; i < nums.size(); ++ i) {
            m[nums[i]].push_back(i);
         }
         for (int i = 0; i < nums.size(); ++ i) {
            if (nums[i] * 2 == target) {
                if (m[nums[i]].size() == 2) {
                    res.push_back(m[nums[i]][0]);
                    res.push_back(m[nums[i]][1]);
                    break;
                }
            }
             else if (m.find(target - nums[i]) != m.end()) {
                 res.push_back(i);
                 res.push_back(m[target-nums[i]][0]);
                break;
                 //return res;
             }
         }
        return res;
    }
};

class Solution:
    def twoSum(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: List[int]
        """
        res = []
        num_indices = dict()
        for index, value in enumerate(nums):
            if value in num_indices:
                num_indices[value].append(index)
            else:
                num_indices[value] = [index]
        for k, v in num_indices.items():
            if k * 2 == target:
                if len(v) == 2:
                    res.extend(v)
                    break
            else:
                if target - k in num_indices:
                    res.append(v[0])
                    res.append(num_indices[target - k][0])
                    break
        return res