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package TwoSum;
import org.junit.Test;
import java.util.*;
/**
* @description: 描述
* @author: dekai.kong (dekai.kong@luckincoffee.com)
* @date: 2018-11-06 17:13
*/
/**
* LeetCode
* https://leetcode.com/problems/3sum/
*Given an array nums of n integers, are there elements a, b, c in nums such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.
*
* Note:
*
* The solution set must not contain duplicate triplets.
*
* Example:
*
* Given array nums = [-1, 0, 1, 2, -1, -4],
*
* A solution set is:
* [
* [-1, 0, 1],
* [-1, -1, 2]
* ]
*/
public class ThreeSum {
public ThreeSum(){
}
//把大于0的都放入map,小于0的相加在>0map查找看看有没有,消重使用set
public List<List<Integer>> threeSumx(int[] nums) {
Long a = System.currentTimeMillis();
List<List<Integer>> resultList = new ArrayList<>();
if(nums.length<3){
return resultList;
}
Map<Integer,Integer> mapKt = new HashMap<>();
Arrays.sort(nums);
int[] numsLeft = new int[nums.length];
int[] numsRigh = new int[nums.length];
Set<String> keySet = new HashSet<>();
int l=0;
int r=0;
for (int i = 0;i<nums.length;i++){
if(nums[i] == 0 && mapKt.getOrDefault(nums[i],0) == 3 || nums[i]!= 0 && mapKt.getOrDefault(nums[i],0) == 2){
continue;
}
if(nums[i]<= 0){
numsLeft[l] = nums[i];
l++;
}else{
numsRigh[r] = nums[i];
r++;
}
mapKt.put(nums[i],mapKt.getOrDefault(nums[i],0)+1);
}
numsLeft = Arrays.copyOfRange(numsLeft, 0, l);
numsRigh = Arrays.copyOfRange(numsRigh, 0, r);
if(numsLeft.length == 0){
return resultList;
}
if(numsLeft.length>=3){
if(numsLeft[numsLeft.length-1] == 0 && numsLeft[numsLeft.length-2] == 0 && numsLeft[numsLeft.length-3] == 0){
resultList.add(Arrays.asList(0, 0,0));
if(numsLeft.length == 3){
return resultList;
}
}
}
for(int i = 0;i<numsLeft.length-1;i++){
for(int j = 1;j<numsLeft.length;j++){
if(i != j && numsLeft[i]<=numsLeft[j]){
if(mapKt.containsKey(0-(numsLeft[i] + numsLeft[j])) && 0-(numsLeft[i] + numsLeft[j])!=0){
int[] temarr = {numsLeft[i],numsLeft[j],0-(numsLeft[i] + numsLeft[j])};
if(!keySet.contains(Arrays.toString(temarr))){
resultList.add(Arrays.asList(numsLeft[i], numsLeft[j],0-(numsLeft[i] + numsLeft[j])));
keySet.add(Arrays.toString(temarr));
}
}
}
}
}
for(int i = 0;i<numsRigh.length-1;i++){
for(int j = 1;j<numsRigh.length;j++){
if(i != j && numsRigh[i]<=numsRigh[j]){
if(mapKt.containsKey(0-(numsRigh[i] + numsRigh[j]))){
int[] temarr = {numsRigh[i],numsRigh[j],0-(numsRigh[i] + numsRigh[j])};
if(!keySet.contains(Arrays.toString(temarr))){
resultList.add(Arrays.asList(numsRigh[i], numsRigh[j],0-(numsRigh[i] + numsRigh[j])));
keySet.add(Arrays.toString(temarr));
}
}
}
}
}
System.out.println("1:"+(System.currentTimeMillis() - a));
return resultList;
}
//最快的方法,来自leetcode
public List<List<Integer>> threeSumX2(int[] nums) {
List<List<Integer>> res = new ArrayList<List<Integer>>();
if(nums.length < 3){
return res;
}else{
Arrays.sort(nums);
for(int i=0;i<nums.length-2;i++){
if(nums[i]>0){
break;
}
if(i>0&&nums[i] == nums[i-1]){
continue;
}
int a1 = i + 1;
int a2 = nums.length-1;
int sum = 0;
int com = 0;
sum = 0 - nums[i];
while(a1<a2){
com = nums[a1] + nums[a2];
if(com == sum){
res.add(new ArrayList<Integer>(Arrays.asList(nums[i],nums[a1],nums[a2])));
while(a1<a2 && nums[a1] == nums[a1+1]){
a1++;
}
while(a1<a2 && nums[a2] == nums[a2-1]){
a2--;
}
a1++;
a2--;
}else if(com < sum){
a1++;
}else{
a2--;
}
}
}
return res;
}
}
//重复率越高越快
public List<List<Integer>> threeSumX3(int[] nums) {
Long a = System.currentTimeMillis();
List<List<Integer>> resultList = new ArrayList<>();
if(nums.length<3){
return resultList;
}
Map<Integer,Integer> mapKt = new HashMap<>();
List<Integer> listKey = new ArrayList<>();
Arrays.sort(nums);
for (int i = 0;i<nums.length;i++){
if(nums[i] == 0 && mapKt.getOrDefault(nums[i],0) == 3 || nums[i]!= 0 && mapKt.getOrDefault(nums[i],0) == 2){
continue;
}
if(mapKt.getOrDefault(nums[i],0) == 0){
listKey.add(nums[i]);
}
mapKt.put(nums[i],mapKt.getOrDefault(nums[i],0)+1);
}
for (int i = 0; i < listKey.size(); i++) {
for(int j = 0; j < listKey.size(); j++){
if(listKey.get(i) <= listKey.get(j)){
if(mapKt.get(listKey.get(i)) == 1 && listKey.get(i) == listKey.get(j)){
continue;
}
if(mapKt.containsKey(0-(listKey.get(i)+listKey.get(j))) ){
if ((0-(listKey.get(i)+listKey.get(j))) > listKey.get(j)){
resultList.add(Arrays.asList(listKey.get(i), listKey.get(j), 0-(listKey.get(i)+listKey.get(j))));
}
else if((0-(listKey.get(i)+listKey.get(j))) == listKey.get(j) && mapKt.get(listKey.get(j)) >= 2){
if(listKey.get(j) == 0){
if(mapKt.get(listKey.get(j)) == 3){
resultList.add(Arrays.asList(listKey.get(i), listKey.get(j), 0-(listKey.get(i)+listKey.get(j))));
}
}else{
resultList.add(Arrays.asList(listKey.get(i), listKey.get(j), 0-(listKey.get(i)+listKey.get(j))));
}
}
}
}
}
}
System.out.println("2:"+(System.currentTimeMillis() - a));
return resultList;
}
@Test
public void testThreeSum(){
// int[] a = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0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// int[] a = {0,1,1};
// int[] a = {-1,0,1};
// int[] a = {-1,0,1,2,-1,-4};
// int[] a = {1,1,-2};
int[] a = {-1,0,1,0};
// int[] a = {-4,-2,1,-5,-4,-4,4,-2,0,4,0,-2,3,1,-5,0};
List<List<Integer>> resultList2 = threeSumx(a);
List<List<Integer>> resultList = threeSumX2(a);
List<List<Integer>> resultList3 = threeSumX3(a);
System.out.println(resultList);
System.out.println(resultList2);
System.out.println(resultList3);
}
/**
* 测试一下回溯能不能解
*/
Set<String> bool;
List<List<Integer>> resx = new ArrayList<List<Integer>>();
public List<List<Integer>> threeSumBackTrace(int[] nums,int n,int k) {
LinkedList<Integer> list = new LinkedList<>();
int cur = 0;
bool = new HashSet<>();
helper(nums,n,k,list,cur);
return resx;
}
public void helper(int[] nums,int n,int k,LinkedList<Integer> list,int cur){
if(list.size()==n&&cur == k){
String s = "";
List nl = new LinkedList<>(list);
Collections.sort(nl);
for (int i = 0; i < nl.size(); i++) {
s+=nl.get(i);
}
if(!bool.contains(s)){
bool.add(s);
resx.add(nl);
}
return;
}
if(list.size()>=n){
return;
}
for(int i = 0;i<nums.length;i++){
if(list.contains(nums[i])){
continue;
}
list.add(nums[i]);
cur+=nums[i];
helper(nums,n,k,list,cur);
cur-=nums[i];
list.removeLast();
}
}
@Test
public void testThreeSumx(){
threeSumBackTrace(new int[]{1,2,3,4,5,6,7,8,9},3,10);
}
}