s0018

src/s0018_4sum.cpp

@@ -0,0 +1,28 @@
+#include "s0018_4sum.hpp"
+
+vector<vector<int>> Solution::fourSum(vector<int>& nums, int target) {
+  int len = nums.size();
+  if (len < 4) {
+    return {};
+  }
+  vector<vector<int>> result{};
+  sort(nums.begin(), nums.end());
+  for (int i{1}; i < len - 2; i++) {
+    for (int j = len - 2; j > i; j--) {
+      for (int x{0}, y = len - 1; x < i && y > j;) {
+        if (nums[x] + nums[y] + nums[i] + nums[j] > target) {
+          y--;
+        } else if (nums[x] + nums[y] + nums[i] + nums[j] < target) {
+          x++;
+        } else {
+          vector<int> v = {nums[x], nums[i], nums[j], nums[y]};
+          if (std::find(result.begin(), result.end(), v) == result.end()) {
+            result.push_back(v);
+          }
+          x++;
+        }
+      }
+    }
+  }
+  return result;
+}