给定一个包含 n 个整数的数组 nums 和一个目标值 target,判断 nums 中是否存在四个元素 a,b,c 和 d ,使得 a + b + c + d 的值与 target 相等?找出所有满足条件且不重复的四元组。
注意:答案中不可以包含重复的四元组。
示例 1:
输入:nums = [1,0,-1,0,-2,2], target = 0
输出:[[-2,-1,1,2],[-2,0,0,2],[-1,0,0,1]]
示例 2:
输入:nums = [], target = 0
输出:[]
提示:
0 <= nums.length <= 200 -109 <= nums[i] <= 109 -109 <= target <= 109
class Solution {
public:
vector<vector<int>> fourSum(vector<int>& nums, int target) {
vector<vector<int>> quadruplets;
if (nums.size() < 4) {
return quadruplets;
}
sort(nums.begin(), nums.end());
int length = nums.size();
for (int i = 0; i < length - 3; i++) {
if (i > 0 && nums[i] == nums[i - 1]) {
continue;
}
if (nums[i] + nums[i + 1] + nums[i + 2] + nums[i + 3] > target) {
break;
}
if (nums[i] + nums[length - 3] + nums[length - 2] + nums[length - 1] < target) {
continue;
}
for (int j = i + 1; j < length - 2; j++) {
if (j > i + 1 && nums[j] == nums[j - 1]) {
continue;
}
if (nums[i] + nums[j] + nums[j + 1] + nums[j + 2] > target) {
break;
}
if (nums[i] + nums[j] + nums[length - 2] + nums[length - 1] < target) {
continue;
}
int left = j + 1, right = length - 1;
while (left < right) {
int sum = nums[i] + nums[j] + nums[left] + nums[right];
if (sum == target) {
quadruplets.push_back({nums[i], nums[j], nums[left], nums[right]});
while (left < right && nums[left] == nums[left + 1]) {
left++;
}
left++;
while (left < right && nums[right] == nums[right - 1]) {
right--;
}
right--;
} else if (sum < target) {
left++;
} else {
right--;
}
}
}
}
return quadruplets;
}
};