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four_sum.js
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four_sum.js
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var fourSum = function (nums, target) {
// Resultant list
const quadruplets = [];
// Base condition
if (nums == undefined || nums.length < 4) {
return quadruplets;
}
// Sort the array
nums.sort((a, b) => a - b);
// Length of the array
const n = nums.length;
// Loop for each element of the array
for (let i = 0; i < n - 3; i++) {
// Check for skipping duplicates
if (i > 0 && nums[i] == nums[i - 1]) {
continue;
}
// Reducing to three sum problem
for (let j = i + 1; j < n - 2; j++) {
// Check for skipping duplicates
if (j != i + 1 && nums[j] == nums[j - 1]) {
continue;
}
// Left and right pointers
let k = j + 1;
let l = n - 1;
// Reducing to two sum problem
while (k < l) {
const currentSum = nums[i] + nums[j] + nums[k] + nums[l];
if (currentSum < target) {
k++;
} else if (currentSum > target) {
l--;
} else {
quadruplets.push([nums[i], nums[j], nums[k], nums[l]]);
k++;
l--;
// Check for skipping duplicates
while (k < l && nums[k] == nums[k - 1]) {
k++;
}
while (k < l && nums[l] == nums[l + 1]) {
l--;
}
}
}
}
}
return quadruplets;
};
console.log(fourSum([1, 0, -1, 0, -2, 2], 0));
console.log(fourSum([], 0));
console.log(fourSum([1, 2, 3, 4], 10));
console.log(fourSum([0, 0, 0, 0], 0));