标签：
Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.
Note:
For example, given array S = {-1 0 1 2 -1 -4},
A solution set is:
(-1, 0, 1)
(-1, -1, 2)
使用两个标记，left和right， 对于每一个值，分别从左向右，从右向左计算
！！ 如何消除duplicate 不太会！！！
public class Solution {
public ArrayList<ArrayList<Integer>> threeSum(int[] num) {
ArrayList<ArrayList<Integer>> result=new ArrayList<ArrayList<Integer>>();
if(num==null||num.length<3){
return result;
}
int sum=0;
Arrays.sort(num);
for(int i=0;i<num.length-2;i++){
if (i != 0 && num[i] == num[i - 1]) {
continue; // to skip duplicate numbers; e.g [0,0,0,0]
}
int left=i+1;
int right=num.length-1;
while(left<right){
sum=num[i]+num[left]+num[right];
if(sum==0){
ArrayList<Integer> temp=new ArrayList<Integer>();
temp.add(num[i]);
temp.add(num[left]);
temp.add(num[right]);
result.add(temp);
left++;
right--;
while (left < right && num[left] == num[left - 1]) { // to skip duplicates
left++;
}
while (left < right && num[right] == num[right + 1]) { // to skip duplicates
right--;
}
}
else if(sum<0){
left++;
}
else{
right--;
}
}
}
return result;
}
}
标签：
原文地址：http://www.cnblogs.com/lilyfindjobs/p/4187957.html
