LeetCode 93 Restore IP address 2023.11.21
class Solution {
public:
vector<string> result;
bool isValid(string s,int start, int end)
{
if(start > end)
return false;
if(s[start] == '0' && start != end)
return false;
int num = 0;
for(int i = start; i <= end; i++)
{
if(s[i] > '9' || s[i] < '0')
return false;
num = num*10 + (s[i] - '0');
if(num > 255)
return false;
}
return true;
}
void backtracking(string &s, int start, int pointNum)
{
if(pointNum == 3)
{
if(isValid(s, start, s.size()-1))
result.push_back(s);
return;
}
for (int i = start; i < s.size()-1; i++)
{
if(isValid(s, start, i))
{
s.insert(s.begin()+i+1, '.');
pointNum++;
backtracking(s, i+2, pointNum);
s.erase(s.begin()+i+1);
pointNum--;
}
else
break;
}
}
vector<string> restoreIpAddresses(string s) {
result.clear();
if(s.empty())
return result;
backtracking(s, 0, 0);
return result;
}
};
LeetCode 78 subset 2023.11.21
class Solution {
public:
vector<int> cur;
vector<vector<int>> result;
void backtracking(vector<int> &nums, int start)
{
result.push_back(cur);
if(start == nums.size())
return;
for (int i = start; i < nums.size(); i++)
{
cur.push_back(nums[i]);
backtracking(nums, i+1);
cur.pop_back();
}
}
vector<vector<int>> subsets(vector<int>& nums) {
cur.clear();
result.clear();
backtracking(nums, 0);
return result;
}
};
LeetCode 90 subset-ii 2023.11.21
class Solution {
public:
vector<int> cur;
set<vector<int>> result;
void backtracking(vector<int> nums, int start)
{
result.insert(cur);
if(start == nums.size())
return;
for (int i = start; i < nums.size(); i++)
{
cur.push_back(nums[i]);
backtracking(nums, i+1);
cur.pop_back();
}
}
vector<vector<int>> subsetsWithDup(vector<int>& nums) {
cur.clear();
result.clear();
sort(nums.begin(), nums.end());
backtracking(nums, 0);
return vector<vector<int>>(result.begin(), result.end());
}
};