Problem
Given an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target.Note:
Elements in a quadruplet (a,b,c,d) must be in non-descending order. (ie, a ≤ b ≤ c ≤ d)
The solution set must not contain duplicate quadruplets.
Example
given array S = {1 0 -1 0 -2 2}, and target = 0.A solution set is:
(-1, 0, 0, 1)
(-2, -1, 1, 2)
(-2, 0, 0, 2)
JavaScript Code
function fourSum(num, target) { num.sort(); var hashSet = []; var result = []; for (var i = 0; i < num.length; i++) { for (var j = i + 1; j < num.length; j++) { var k = j + 1; var l = num.length - 1; while (k < l) { var sum = num[i] + num[j] + num[k] + num[l]; if (sum > target) { l--; } else if (sum < target) { k++; } else if (sum == target) { var temp = []; temp.push(num[i]); temp.push(num[j]); temp.push(num[k]); temp.push(num[l]); if (hashSet[temp] == null) { hashSet.push(temp); result.push(temp); } k++; l--; } } } } return result; } console.log(fourSum([1,0,-1,0,-2,2], 1));
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