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:
给定数组 nums = [1, 0, -1, 0, -2, 2],和 target = 0。
满足要求的四元组集合为:
[
[-1, 0, 0, 1],
[-2, -1, 1, 2],
[-2, 0, 0, 2]
]
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class algorithm {
public List<List<Integer>> fourSum(int[] nums, int target) {
List<List<Integer>> lists = new ArrayList<>();
Arrays.sort(nums);
/*for (int num : nums) {
System.out.printf(num+" ");
}
System.out.println();*/
int n = nums.length - 1;
for (int i = 0; i <= n; i++) {
int last_j = 0;
if (i != 0 && nums[i] == nums[i-1]) {
continue;
}
for (int j = i+1; j <= n; j++) {
if (nums[j] == nums[last_j] && last_j != 0){
continue;
}
last_j = j;
int l = j + 1;
int r = n;
int last_l = 0;
while (l < r){
if (nums[last_l] == nums[l] && last_l != 0) {
l++;
continue;
}
if (nums[i] + nums[j] + nums[l] + nums[r] < target){
//System.out.println("lllll");
l++;
}else if (nums[i] + nums[j] + nums[l] + nums[r] > target){
//System.out.println("rrrrr");
r--;
}else {
List<Integer> list = new ArrayList<>();
list.add(nums[i]);
list.add(nums[j]);
list.add(nums[l]);
list.add(nums[r]);
lists.add(list);
last_l = l;
l++;
r--;
}
}
}
}
return lists;
}
public static void main(String[] args) {
int[] nums = {1, 0, -1, 0, -2, 2};
int target = 0;
List<List<Integer>> lists = new algorithm().fourSum(nums, target);
//System.out.println("===============");
for (int i = 0; i < lists.size(); i++) {
for (Integer integer : lists.get(i)) {
System.out.print(integer+" ");
}
System.out.println();
}
}
}