LeetCode: Two Sum

坑爹的多数次过。。

 1 class Solution {

 2 public:

 3     vector<int> twoSum(vector<int> &numbers, int target) {

 4         // Start typing your C/C++ solution below

 5         // DO NOT write int main() function

 6         int left = 0;

 7         int right = numbers.size() - 1;

 8         vector<int> ret;

 9         map<int, vector<int>> S;

10         for (int i = 0; i < numbers.size(); i++) S[numbers[i]].push_back(i+1);

11         sort(numbers.begin(), numbers.end());

12         while (left < right) {

13             if (numbers[left] + numbers[right] == target) {

14                 if (S[numbers[left]].size() > 1) {

15                     ret.push_back(S[numbers[left]][0]);

16                     ret.push_back(S[numbers[right]][1]);

17                     return ret;

18                 }

19                 int a = S[numbers[left]][0];

20                 int b = S[numbers[right]][0];

21                 if (a > b) {

22                     ret.push_back(b);

23                     ret.push_back(a);

24                 }

25                 else {

26                     ret.push_back(a);

27                     ret.push_back(b);

28                 }

29                 return ret;

30             }

31             if (numbers[left] + numbers[right] < target) left++;

32             else right--;

33         }

34     }

35 };

 后来写了另外一段代码，更清楚点

 1 class Solution {

 2 public:

 3     vector<int> twoSum(vector<int> &numbers, int target) {

 4         // Start typing your C/C++ solution below

 5         // DO NOT write int main() function

 6         map<int, int> S;

 7         for (int i = 0; i < numbers.size(); i++) S[i+1] = numbers[i];

 8         sort(numbers.begin(), numbers.end());

 9         int left = 0;

10         int right = numbers.size()-1;

11         while (left < right) {

12             int sum = numbers[left] + numbers[right];

13             if (sum == target) break;

14             if (sum < target) left++;

15             else right--;

16         }

17         vector<int> ret;

18         int first, second;

19         first = second = 0;

20         for (map<int, int>::iterator it = S.begin(); it != S.end(); it++) {

21             if (numbers[left] == it->second || numbers[right] == it->second) {

22                 if (!first) first = it->first;

23                 else second = it->first;

24             }

25         }

26         if (first > second) swap(first, second);

27         ret.push_back(first);

28         ret.push_back(second);

29         return ret;

30     }

31 };

 C#

 1 public class Solution {

 2     public int[] TwoSum(int[] nums, int target) {

 3         Dictionary<int, int> S = new Dictionary<int, int>();

 4         for (int i = 0; i < nums.Length; i++) S.Add(i+1, nums[i]);

 5         Array.Sort(nums);

 6         int left = 0, right = nums.Length-1;

 7         while (left < right) {

 8             int sum = nums[left] + nums[right];

 9             if (sum == target) break;

10             if (sum < target) left++;

11             else right--;

12         }

13         int[] ans = new int[2];

14         int first = 0, second = 0;

15         foreach (var v in S) {

16             if (nums[left] == v.Value || nums[right] == v.Value) {

17                 if (first == 0) first = v.Key;

18                 else second = v.Key;

19             }

20         }

21         if (first > second) {

22             int tmp = first;

23             first = second;

24             second = tmp;

25         }

26         ans[0] = first;

27         ans[1] = second;

28         return ans;

29     }

30 }

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