leetcode-study/3sum/YoungSeok-Choi.java at main · DaleStudy/leetcode-study · GitHub

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import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collections;

import java.util.HashSet;

import java.util.List;

import java.util.Set;

// NOTE: 실행시간 1.5초..

// 시간 복잡도: O(n^2)

class Solution {

public List<List<Integer>> threeSum(int[] nums) {

Arrays.sort(nums);

Set<List<Integer>> result = new HashSet<>();

for(int i = 0; i < nums.length - 2; i++) {

int startIdx = i + 1;

int endIdx = nums.length - 1;

while(startIdx < endIdx) {

int sum = nums[i] + nums[startIdx] + nums[endIdx];

if(sum == 0) {

result.add(Arrays.asList(nums[i], nums[startIdx], nums[endIdx]));

}

if(sum > 0) {

endIdx--;

} else {

startIdx++;

}

return new ArrayList<>(result);

}

// 309 / 314 testcases passed Time Limit Exceeded

// NOTE: 시간복잡도 O(n^3)

class WrongSolution {

public List<List<Integer>> threeSum(int[] nums) {

Set<List<Integer>> res = new HashSet<>();

List<Integer> temp = new ArrayList<>();

temp.remove(3);

for(int i = 0; i < nums.length; i++) {

for(int j = 0; j < i; j++) {

for(int k = 0; k < j; k++) {

if((nums[i] + nums[j] + nums[k]) == 0) {

List<Integer> solution = Arrays.asList(nums[i], nums[j], nums[k]);

Collections.sort(solution);

res.add(solution);

}

return new ArrayList<>(res);

}

leetcode-study/3sum/YoungSeok-Choi.java at main · DaleStudy/leetcode-study · GitHub

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leetcode-study/3sum/YoungSeok-Choi.java at main · DaleStudy/leetcode-study · GitHub

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