From 8a167ebab112b4f7701bfc84db5bdd2d46f0b1ff Mon Sep 17 00:00:00 2001
From: SquidSpirit <squid@squidspirit.com>
Date: Thu, 20 Feb 2025 23:35:00 +0800
Subject: [PATCH] feat: 18_4sum

---
 18_4sum/main.cpp | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100644 18_4sum/main.cpp

diff --git a/18_4sum/main.cpp b/18_4sum/main.cpp
new file mode 100644
index 0000000..627891a
--- /dev/null
+++ b/18_4sum/main.cpp
@@ -0,0 +1,36 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+class Solution {
+   public:
+    vector<vector<int>> fourSum(vector<int>& nums, int target) {
+        set<vector<int>> resultSet;
+
+        sort(nums.begin(), nums.end());
+
+        for (int i = 0; i < nums.size(); i++) {
+            for (int j = i + 1; j < nums.size(); j++) {
+                int l = j + 1, r = nums.size() - 1;
+
+                while (l < r) {
+                    long long sum = (long long)nums[i] + nums[j] + nums[l] + nums[r];
+                    if (sum < target) {
+                        l++;
+                    } else if (sum > target) {
+                        r--;
+                    } else {
+                        resultSet.insert({nums[i], nums[j], nums[l], nums[r]});
+                        l++;
+                    }
+                }
+            }
+        }
+
+        vector<vector<int>> result;
+        for (auto& e : resultSet) {
+            result.emplace_back(e);
+        }
+
+        return result;
+    }
+};