Leetcode#15 3Sum

Difficulty:Medium

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:

Elements in a triplet (a,b,c) must be in non-descending order. (ie, a ≤ b ≤ c)
The solution set must not contain duplicate triplets.

For example, given array S = {-1 0 1 2 -1 -4},

A solution set is:
(-1, 0, 1)
(-1, -1, 2)

折腾了好久终于debug出来了。

vector<vector<int> > threeSum(vector<int>& nums) {
vector<vector<int> > ans;
int len =  nums.size();
sort(nums.begin(),nums.end());

for(int i = 0; i<len-2;i++){
int tar = 0 - nums[i];
int beg = i+1, en = len-1;
if(nums[i]==nums[i-1]&&i>0)
continue;
while(en>beg){
if(nums[beg]==nums[beg-1]&&beg>i+1)
{beg++;
continue;}
if(nums[en]==nums[en+1]&&en<len-1){
en--;
continue;}

if(nums[en]+nums[beg]<tar){
beg++;
}
else if(nums[en]+nums[beg]>tar){
en--;
}
else
{
vector<int> tmp;
tmp.push_back(nums[i]);
tmp.push_back(nums[beg]);
tmp.push_back(nums[en]);
ans.push_back(tmp);
//cout<<"结果："<<nums[i]<<"  "<<nums[beg]<<"  "<<nums[en]<<"  "<<endl;
beg++;                }

}
}
return ans;
}