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feat: add solutions to lcci problem: No.16.24
No.16.24.Pairs With Sum
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‎lcci/16.24.Pairs With Sum/README.md

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## 题目描述
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<!-- 这里写题目描述 -->
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<p>设计一个算法，找出数组中两数之和为指定值的所有整数对。一个数只能属于一个数对。</p>
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<p><strong>示例 1:</strong></p>
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<pre><strong>输入:</strong> nums = [5,6,5], target = 11
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<ul>
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<li><code>nums.length &lt;= 100000</code></li>
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</ul>
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## 解法
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<!-- 这里可写通用的实现逻辑 -->
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**方法一：哈希表**
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我们可以使用哈希表来存储数组中的元素，键为数组中的元素，值为该元素出现的次数。
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遍历数组，对于每个元素 $x$，我们计算 $y = target - x$，如果哈希表中存在 $y$，则说明存在一对数 $(x, y)$，我们将其加入答案，并减少 $y$ 的出现次数。如果哈希表中不存在 $y$，则说明不存在这样的数对，我们将 $x$ 的出现次数加 $1$。
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遍历结束后，即可得到答案。
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时间复杂度 $O(n)$，空间复杂度 $O(n)$。其中 $n$ 为数组的长度。
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<!-- tabs:start -->
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### **Python3**
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<!-- 这里可写当前语言的特殊实现逻辑 -->
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```python
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class Solution:
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def pairSums(self, nums: List[int], target: int) -> List[List[int]]:
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cnt = Counter()
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ans = []
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for x in nums:
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y = target - x
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if cnt[y]:
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cnt[y] -= 1
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ans.append([x, y])
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else:
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cnt[x] += 1
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return ans
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```
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````
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### **Java**
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<!-- 这里可写当前语言的特殊实现逻辑 -->
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```java
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class Solution {
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public List<List<Integer>> pairSums(int[] nums, int target) {
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Map<Integer, Integer> cnt = new HashMap<>();
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List<List<Integer>> ans = new ArrayList<>();
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for (int x : nums) {
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int y = target - x;
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if (cnt.containsKey(y)) {
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ans.add(List.of(x, y));
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if (cnt.merge(y, -1, Integer::sum) == 0) {
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cnt.remove(y);
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}
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} else {
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cnt.merge(x, 1, Integer::sum);
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}
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}
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return ans;
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}
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}
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```
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````
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### **C++**
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```cpp
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class Solution {
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public:
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vector<vector<int>> pairSums(vector<int>& nums, int target) {
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unordered_map<int, int> cnt;
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vector<vector<int>> ans;
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for (int x : nums) {
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int y = target - x;
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if (cnt[y]) {
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--cnt[y];
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ans.push_back({x, y});
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} else {
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++cnt[x];
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}
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}
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return ans;
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}
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};
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```
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### **Go**
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```go
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func pairSums(nums []int, target int) (ans [][]int) {
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cnt := map[int]int{}
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for _, x := range nums {
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y := target - x
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if cnt[y] > 0 {
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cnt[y]--
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ans = append(ans, []int{x, y})
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} else {
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cnt[x]++
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}
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}
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return
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}
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```
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### **...**
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‎lcci/16.24.Pairs With Sum/README_EN.md

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### **Python3**
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```python
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class Solution:
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def pairSums(self, nums: List[int], target: int) -> List[List[int]]:
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cnt = Counter()
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ans = []
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for x in nums:
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y = target - x
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if cnt[y]:
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cnt[y] -= 1
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ans.append([x, y])
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else:
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cnt[x] += 1
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return ans
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```
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### **Java**
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```java
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class Solution {
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public List<List<Integer>> pairSums(int[] nums, int target) {
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Map<Integer, Integer> cnt = new HashMap<>();
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List<List<Integer>> ans = new ArrayList<>();
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for (int x : nums) {
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int y = target - x;
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if (cnt.containsKey(y)) {
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ans.add(List.of(x, y));
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if (cnt.merge(y, -1, Integer::sum) == 0) {
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cnt.remove(y);
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}
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} else {
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cnt.merge(x, 1, Integer::sum);
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}
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}
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return ans;
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}
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}
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```
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### **C++**
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```cpp
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class Solution {
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public:
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vector<vector<int>> pairSums(vector<int>& nums, int target) {
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unordered_map<int, int> cnt;
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vector<vector<int>> ans;
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for (int x : nums) {
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int y = target - x;
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if (cnt[y]) {
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--cnt[y];
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ans.push_back({x, y});
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} else {
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++cnt[x];
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}
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}
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return ans;
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}
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};
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```
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### **Go**
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```go
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func pairSums(nums []int, target int) (ans [][]int) {
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cnt := map[int]int{}
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for _, x := range nums {
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y := target - x
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if cnt[y] > 0 {
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cnt[y]--
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ans = append(ans, []int{x, y})
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} else {
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cnt[x]++
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}
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}
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return
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}
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```
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### **...**

‎lcci/16.24.Pairs With Sum/Solution.cpp

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class Solution {
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public:
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vector<vector<int>> pairSums(vector<int>& nums, int target) {
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unordered_map<int, int> cnt;
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vector<vector<int>> ans;
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for (int x : nums) {
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int y = target - x;
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if (cnt[y]) {
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--cnt[y];
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ans.push_back({x, y});
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} else {
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++cnt[x];
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}
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}
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return ans;
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}
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};

‎lcci/16.24.Pairs With Sum/Solution.go

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func pairSums(nums []int, target int) (ans [][]int) {
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cnt := map[int]int{}
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for _, x := range nums {
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y := target - x
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if cnt[y] > 0 {
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cnt[y]--
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ans = append(ans, []int{x, y})
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} else {
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cnt[x]++
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}
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}
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return
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}

‎lcci/16.24.Pairs With Sum/Solution.java

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class Solution {
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public List<List<Integer>> pairSums(int[] nums, int target) {
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Map<Integer, Integer> cnt = new HashMap<>();
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List<List<Integer>> ans = new ArrayList<>();
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for (int x : nums) {
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int y = target - x;
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if (cnt.containsKey(y)) {
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ans.add(List.of(x, y));
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if (cnt.merge(y, -1, Integer::sum) == 0) {
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cnt.remove(y);
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}
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} else {
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cnt.merge(x, 1, Integer::sum);
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}
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}
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return ans;
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}
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}

‎lcci/16.24.Pairs With Sum/Solution.py

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class Solution:
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def pairSums(self, nums: List[int], target: int) -> List[List[int]]:
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cnt = Counter()
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ans = []
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for x in nums:
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y = target - x
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if cnt[y]:
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cnt[y] -= 1
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ans.append([x, y])
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else:
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cnt[x] += 1
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return ans

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