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Copy paththree-num-sum.js
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74 lines (65 loc) · 1.96 KB
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// Time O(n^2) | space O(n) where n is the number of three sums
function threeNumberSum(array, targetSum) {
array.sort((a, b) => a - b);
const result = [];
for (let i = 0; i < array.length - 1; i++) {
const firstNumber = array[i];
let leftPointer = i + 1;
let rightPointer = array.length - 1;
while (leftPointer < rightPointer) {
const leftNumber = array[leftPointer];
const rightNumber = array[rightPointer];
if (firstNumber + leftNumber + rightNumber === targetSum) {
result.push([firstNumber, leftNumber, rightNumber]);
leftPointer++;
rightPointer--;
} else if (firstNumber + leftNumber + rightNumber < targetSum) {
leftPointer++;
} else {
rightPointer--;
}
}
}
return result;
}
const array = [12, 3, 1, 2, -6, 5, 0, -8, -1, 6];
const targetSum = 0;
// This solution avoids duplicates
/**
* @param {number[]} nums
* @return {number[][]}
*/
// Time O(n^2)
// Space O(n)
var threeSum = function (nums) {
nums.sort((a, b) => a - b);
let triplets = [];
for (let i = 0; i < nums.length - 2; i++) {
if (i > 0 && nums[i] == nums[i - 1]) continue; //avoid duplicates
let leftPointer = i + 1;
let rightPointer = nums.length - 1;
while (leftPointer < rightPointer) {
let currentSum = nums[i] + nums[leftPointer] + nums[rightPointer];
if (currentSum === 0) {
triplets.push([nums[i], nums[leftPointer], nums[rightPointer]]);
leftPointer++;
rightPointer--;
while (
leftPointer < rightPointer &&
nums[leftPointer] == nums[leftPointer - 1]
)
leftPointer++; //avoid duplicates
while (
leftPointer < rightPointer &&
nums[rightPointer] == nums[rightPointer + 1]
)
rightPointer--; //avoid duplicates
} else if (currentSum > 0) {
rightPointer--;
} else if (currentSum < 0) {
leftPointer++;
}
}
}
return triplets;
};