LeetCode: Two Sum

坑爹的多数次过。。

class Solution {
public:
    vector<int> twoSum(vector<int> &numbers, int target) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        int left = 0;
        int right = numbers.size() - 1;
        vector<int> ret;
        map<int, vector<int>> S;
        for (int i = 0; i < numbers.size(); i++) S[numbers[i]].push_back(i+1);
        sort(numbers.begin(), numbers.end());
        while (left < right) {
            if (numbers[left] + numbers[right] == target) {
                if (S[numbers[left]].size() > 1) {
                    ret.push_back(S[numbers[left]][0]);
                    ret.push_back(S[numbers[right]][1]);
                    return ret;
                }
                int a = S[numbers[left]][0];
                int b = S[numbers[right]][0];
                if (a > b) {
                    ret.push_back(b);
                    ret.push_back(a);
                }
                else {
                    ret.push_back(a);
                    ret.push_back(b);
                }
                return ret;
            }
            if (numbers[left] + numbers[right] < target) left++;
            else right--;
        }
    }
};

 后来写了另外一段代码，更清楚点

class Solution {
public:
    vector<int> twoSum(vector<int> &numbers, int target) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        map<int, int> S;
        for (int i = 0; i < numbers.size(); i++) S[i+1] = numbers[i];
        sort(numbers.begin(), numbers.end());
        int left = 0;
        int right = numbers.size()-1;
        while (left < right) {
            int sum = numbers[left] + numbers[right];
            if (sum == target) break;
            if (sum < target) left++;
            else right--;
        }
        vector<int> ret;
        int first, second;
        first = second = 0;
        for (map<int, int>::iterator it = S.begin(); it != S.end(); it++) {
            if (numbers[left] == it->second || numbers[right] == it->second) {
                if (!first) first = it->first;
                else second = it->first;
            }
        }
        if (first > second) swap(first, second);
        ret.push_back(first);
        ret.push_back(second);
        return ret;
    }
};

 C#

public class Solution {
    public int[] TwoSum(int[] nums, int target) {
        Dictionary<int, int> S = new Dictionary<int, int>();
        for (int i = 0; i < nums.Length; i++) S.Add(i+1, nums[i]);
        Array.Sort(nums);
        int left = 0, right = nums.Length-1;
        while (left < right) {
            int sum = nums[left] + nums[right];
            if (sum == target) break;
            if (sum < target) left++;
            else right--;
        }
        int[] ans = new int[2];
        int first = 0, second = 0;
        foreach (var v in S) {
            if (nums[left] == v.Value || nums[right] == v.Value) {
                if (first == 0) first = v.Key;
                else second = v.Key;
            }
        }
        if (first > second) {
            int tmp = first;
            first = second;
            second = tmp;
        }
        ans[0] = first;
        ans[1] = second;
        return ans;
    }
}