3SumJan 18 '128685 / 33750
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)
class Solution {
public:
vector<vector<int> > threeSum(vector<int> &num) {
sort(num.begin(), num.end());
vector<vector<int> > res;
int len = num.size();
for (int i = 0; i < len - 2; i++) {
if (i > 0 && num[i] == num[i-1]) continue;
int a = i+1, b = len -1;
int t = -num[i];
while (a < b) {
if (num[a] + num[b] == t) {
int tmp[3] = {-t, num[a], num[b]};
vector<int> tmp2(tmp, tmp+3);
res.push_back(std::move(tmp2));
while (a < b && num[a] == num[a+1]) a++;
a++;
while (a < b && num[b] == num[b-1]) b--;
b--;
}
else if (num[a] + num[b] > t) {
b--;
} else a++;
}
}
return res;
}
};