依旧很长很慢。。。最好还是参考答案里50ms那个程序,我的这个想的复杂了,懒得解释
bool f(int left, int right, int value, vector<int>& nums)
{
if(left > right)return false;
int mid = (left + right) / 2;
if(nums[mid] == value)return true;
else if(left == right)return false;
else if(nums[mid] < value)return f(mid + 1, right, value, nums);
else return f(left, mid, value, nums);
}
class Solution {
public:
vector<vector<int> > threeSum(vector<int>& nums) {
vector<vector<int> > ans;
//if(nums.size() < 3)return ans;
sort(nums.begin(), nums.end());
int size = nums.size();
for (int i = 0; i < size && nums[i] <= 0; ++i)
{
for (int j = size - 1; j != i && nums[j] >= 0; j--)
{
//cout << i << " " << j << endl;
if(0 - nums[i] - nums[j] < nums[i] || 0 - nums[i] - nums[j] > nums[j])
continue;
if(f(i + 1, j - 1, 0 - nums[i] - nums[j], nums)){
vector<int> t(3, 0);
t[0] = nums[i]; t[1] = nums[j]; t[2] = 0 - nums[i] - nums[j];
ans.push_back(t);
}
while(j - 1 > 0 && nums[j - 1] == nums[j])j--;
}
while(i + 1 < nums.size() && nums[i + 1] == nums[i]) i++;
}
//cout << "size " << ans.size() << endl;
return ans;
}
};