leetcode

Mix of various problems

18 files changed, 339 insertions(+), 4 deletions(-)

diff --git a/ Problems/0023.cpp b/ Problems/0023.cpp

@@ -0,0 +1,22 @@

class Solution {

public:

ListNode *mergeKLists(vector<ListNode *> &lists) {

ListNode *dummy, *tmp;

tmp = dummy = new ListNode;

while (true) {

int mini = INT_MAX, index = -1;

for (int i = 0; i < lists.size(); i++) {

if (lists[i] && lists[i]->val < mini) {

index = i;

mini = lists[i]->val;

}

}

if (index == -1) break;

ListNode *t = lists[index];

lists[index] = lists[index]->next;

tmp = tmp->next = t;

}

return dummy->next;

}

};

diff --git a/ Problems/0025.cpp b/ Problems/0025.cpp

@@ -0,0 +1,21 @@

class Solution {

public:

ListNode *reverseKGroup(ListNode *head, int k) {

stack<ListNode *> st;

ListNode *tmp, *dummy, *next;

tmp = dummy = new ListNode(-1, nullptr);

for (ListNode *p = head; p; p = next) {

next = p->next;

st.push(p);

if (st.size() == k) {

while (!st.empty()) {

tmp = tmp->next = st.top();

st.pop();

}

tmp->next = next;

}

}

return dummy->next;

}

};

diff --git a/ Problems/0049.cpp b/ Problems/0049.cpp

@@ -0,0 +1,20 @@

class Solution {

public:

vector<vector<string>> groupAnagrams(vector<string> &strs) {

vector<vector<string>> res;

unordered_map<unsigned long long, int> um;

for (int i = 0; i < strs.size(); i++) {

unsigned long long hash = 0;

vector<int> m(26, 0);

for (char c : strs[i]) m[c - 'a']++;

for (int i = 0; i < 26; i++) hash = hash * 100 + m[i];

if (um.find(hash) == um.end()) {

um[hash] = res.size();

res.push_back({strs[i]});

} else

res[um[hash]].push_back(strs[i]);

}

return res;

}

};

diff --git a/ Problems/0055.cpp b/ Problems/0055.cpp

@@ -0,0 +1,8 @@

class Solution {

public:

bool canJump(vector<int> &nums) {

int n = nums.size(), limit = 0;

for (int i = 0; i <= limit && i < n; i++) limit = max(limit, i + nums[i]);

return limit >= n - 1;

}

};

diff --git a/ Problems/0122.cpp b/ Problems/0122.cpp

@@ -0,0 +1,13 @@

class Solution {

public:

int maxProfit(vector<int> &prices) {

int profit = 0;

prices.push_back(INT_MIN);

for (int i = 0, j = 0; i < prices.size() - 1; i++) {

while (prices[j] < prices[j + 1]) j++;

profit += prices[j] - prices[i];

i = j++;

}

return profit;

}

};

diff --git a/ Problems/0125.cpp b/ Problems/0125.cpp

@@ -0,0 +1,17 @@

class Solution {

public:

bool isPalindrome(string s) {

int i = 0, j = s.size() - 1;

while (i < j) {

if (!isalnum(s[j]))

j--;

else if (!isalnum(s[i]))

i++;

else if (tolower(s[i]) != tolower(s[j]))

return false;

else

i++, j--;

}

return true;

}

};

diff --git a/ Problems/0155.cpp b/ Problems/0155.cpp

@@ -0,0 +1,12 @@

class MinStack {

stack<pair<int, int>> st;

public:

MinStack() {}

void push(int val) {

st.push({val, !st.size() ? val : min(val, st.top().second)});

}

void pop() { st.pop(); }

int top() { return st.top().first; }

int getMin() { return st.top().second; }

};

diff --git a/ Problems/0217.cpp b/ Problems/0217.cpp

@@ -0,0 +1,12 @@

class Solution {

public:

bool containsDuplicate(vector<int> &nums) {

unordered_set<int> us;

for (int n : nums)

if (us.count(n))

return true;

else

us.insert(n);

return false;

}

};

diff --git a/ Problems/0238.cpp b/ Problems/0238.cpp

@@ -0,0 +1,17 @@

class Solution {

public:

vector<int> productExceptSelf(vector<int> &nums) {

int n = nums.size();

vector<int> answer(n, 1);

int acc1 = 1, acc2 = 1;

for (int i = 0, j = n - 1; i < n; i++, j--) {

answer[i] *= acc1;

answer[j] *= acc2;

acc1 *= nums[i];

acc2 *= nums[j];

}

return answer;

}

};

diff --git a/ Problems/0242.cpp b/ Problems/0242.cpp

@@ -0,0 +1,14 @@

class Solution {

public:

bool isAnagram(string s, string t) {

if (s.size() != t.size()) return false;

vector<int> um(26, 0);

for (char c : s) um[c - 'a']++;

for (char c : t)

if (!um[c - 'a'])

return false;

else

um[c - 'a']--;

return true;

}

};

diff --git a/ Problems/0287.cpp b/ Problems/0287.cpp

@@ -0,0 +1,18 @@

class Solution {

public:

int findDuplicate(vector<int> &nums) {

int slow = 0, fast = 0;

while (true) {

fast = nums[nums[fast]];

slow = nums[slow];

if (fast == slow) {

fast = 0;

while (fast != slow) {

fast = nums[fast];

slow = nums[slow];

}

return fast;

}

}

}

};

diff --git a/ Problems/0347.cpp b/ Problems/0347.cpp

@@ -0,0 +1,29 @@

struct elem {

static void reset() { id_cnt = 0; }

static int id_cnt;

int id = id_cnt++, count = 0;

void operator++(int) { count++; }

friend bool operator<(const elem &e1, const elem &e2) {

return e1.count > e2.count;

}

friend ostream &operator<<(ostream &os, const elem &e) {

return os << e.id << ": " << e.count;

}

};

int elem::id_cnt = 0;

class Solution {

const int size = 20002;

const int mod = 10000;

public:

vector<int> topKFrequent(vector<int> &nums, int k) {

elem::reset();

vector<elem> um(size);

for (int n : nums) um[n + mod]++;

sort(um.begin(), um.end());

vector<int> res;

for (int i = 0; i < k; i++) res.push_back(um[i].id - mod);

return res;

}

};

diff --git a/ Problems/0802.cpp b/ Problems/0802.cpp

@@ -0,0 +1,39 @@

class Solution {

public:

vector<int> eventualSafeNodes(vector<vector<int>> &graph) {

int n = graph.size();

vector<int> res;

vector<bool> visited(n, false);

vector<bool> safe(n, false);

stack<int> st;

for (int i = 0; i < n; i++) {

if (visited[i]) continue;

st.push(i);

while (!st.empty()) {

int root = st.top();

st.pop();

if (root == -1) {

root = st.top();

st.pop();

bool s = true;

for (int c : graph[root])

if (!safe[c]) {

s = false;

break;

}

safe[root] = s;

continue;

}

if (visited[root]) continue;

visited[root] = true;

st.push(root);

st.push(-1);

for (int c : graph[root])

if (!visited[c]) st.push(c);

}

}

for (int i = 0; i < n; i++)

if (safe[i]) res.push_back(i);

return res;

}

};

diff --git a/ Problems/0886.cpp b/ Problems/0886.cpp

@@ -0,0 +1,30 @@

class Solution {

public:

bool possibleBipartition(int n, vector<vector<int>> &dislikes) {

vector<vector<int>> adj(n + 1, vector<int>());

for (auto &p : dislikes) {

adj[p[0]].push_back(p[1]);

adj[p[1]].push_back(p[0]);

}

stack<int> st;

vector<int> color(n + 1, -1);

for (int i = 1; i <= n; i++) {

if (color[i] != -1) continue;

color[i] = 0;

st.push(i);

while (!st.empty()) {

int root = st.top();

st.pop();

for (int child : adj[root]) {

if (color[child] == color[root]) return false;

if (color[child] == -1) {

color[child] = !color[root];

st.push(child);

}

}

}

}

return true;

}

};

diff --git a/ Problems/1319.cpp b/ Problems/1319.cpp

@@ -13,8 +13,6 @@ public: } void join(int x, int y) {

x = find(x), y = find(y);

if (x != y) { if (rank[x] > rank[y]) swap(x, y);

@@ -36,10 +34,11 @@ public: int count = 0; UnionFind uf(n); for (auto &edge : connections) {

if (uf.find(edge[0]) == uf.find(edge[1]))

int x = uf.find(edge[0]), y = uf.find(edge[1]);

if (x == y)

count++; else

uf.join(edge[0], edge[1]);

uf.join(x, y);

} return count < uf.count() - 1 ? -1 : uf.count() - 1; }

diff --git a/ Problems/1615.cpp b/ Problems/1615.cpp

@@ -0,0 +1,17 @@

class Solution {

public:

int maximalNetworkRank(int n, vector<vector<int>> &roads) {

vector<unordered_set<int>> adj(n, unordered_set<int>());

for (auto &p : roads) {

adj[p[0]].insert(p[1]);

adj[p[1]].insert(p[0]);

}

int res = 0;

for (int i = 0; i < n; i++)

for (int j = i + 1; j < n; j++)

res = max(res, (int)(adj[i].size() + adj[j].size() - adj[i].count(j)));

return res;

}

};

diff --git a/ Problems/2368.cpp b/ Problems/2368.cpp

@@ -0,0 +1,31 @@

class Solution {

public:

int reachableNodes(int n, vector<vector<int>> &edges,

vector<int> &restricted) {

unordered_set<int> rest(restricted.begin(), restricted.end());

vector<vector<int>> adj(n, vector<int>());

for (auto &p : edges) {

if (rest.count(p[0]) || rest.count(p[1])) continue;

adj[p[0]].push_back(p[1]);

adj[p[1]].push_back(p[0]);

}

int res = 0;

stack<int> st;

vector<bool> visited(n, false);

st.push(0);

visited[0] = true;

while (!st.empty()) {

int root = st.top();

st.pop();

res++;

for (int c : adj[root])

if (!visited[c]) {

st.push(c);

visited[c] = true;

}

}

return res;

}

};

diff --git a/ README.md b/ README.md

@@ -19,13 +19,17 @@ if you have any questions. | 0019 | Medium | [Remove Nth Node From the End of List](Problems/0019.cpp) | | 0020 | Easy | [Valid Parentheses](Problems/0020.cpp) | | 0021 | Easy | [Merge Two Sorted Lists](Problems/0021.cpp) |

| 0023 | Hard | [Merge k Sorted Lists](Problems/0023.cpp) |

| 0024 | Medium | [Swap Nodes in Pairs](Problems/0024.cpp) |

| 0025 | Hard | [Reverse Nodes in k-Group](Problems/0025.cpp) |

| 0026 | Easy | [Remove Duplicates from Sorted Array](Problems/0026.cpp) | | 0027 | Easy | [Remove Element](Problems/0027.cpp) | | 0028 | Medium | [Find the Index of the First Occurrence in a String](Problems/0028.cpp) | | 0036 | Medium | [Valid Sudoku](Problems/0036.cpp) | | 0043 | Medium | [Multiply Strings](Problems/0043.cpp) |

| 0049 | Medium | [Group Anagrams](Problems/0049.cpp) |

| 0054 | Medium | [Spiral Matrix](Problems/0054.cpp) |

| 0055 | Medium | [Jump Game](Problems/0055.cpp) |

| 0059 | Medium | [Spiral Matrix II](Problems/0059.cpp) | | 0061 | Medium | [Rotate List](Problems/0061.cpp) | | 0066 | Easy | [Plus One](Problems/0066.cpp) |

@@ -48,7 +52,9 @@ if you have any questions. | 0118 | Easy | [Pascal's Triangle](Problems/0118.cpp) | | 0119 | Easy | [Pascal's Triangle II](Problems/0119.cpp) | | 0121 | Easy | [Best Time to Buy and Sell Stock](Problems/0121.cpp) |

| 0122 | Medium | [Best Time to Buy and Sell Stock II](Problems/0122.cpp) |

| 0124 | Hard | [Binary Tree Maximum Path Sum](Problems/0124.cpp) |

| 0125 | Easy | [Valid Palindrome](Problems/0125.cpp) |

| 0133 | Medium | [Clone Graph](Problems/0133.cpp) | | 0138 | Medium | [Copy List with Random Pointer](Problems/0138.cpp) | | 0141 | Easy | [Linked List Cycle](Problems/0141.cpp) |

@@ -57,6 +63,7 @@ if you have any questions. | 0145 | Easy | [Binary Tree Postorder Traversal](Problems/0145.cpp) | | 0150 | Medium | [Evaluate Reverse Polish Notation](Problems/0150.cpp) | | 0151 | Medium | [Reverse Words in a String](Problems/0151.cpp) |

| 0155 | Medium | [Min Stack](Problems/0155.cpp) |

| 0160 | Easy | [Intersection of Two Linked Lists](Problems/0160.cpp) | | 0167 | Medium | [Two Sum II - Input Array Is Sorted](Problems/0167.cpp) | | 0189 | Medium | [Rotate Array](Problems/0189.cpp) |

@@ -66,20 +73,25 @@ if you have any questions. | 0203 | Easy | [Remove Linked List Elements](Problems/0203.cpp) | | 0206 | Easy | [Reverse Linked List](Problems/0206.cpp) | | 0209 | Medium | [Minimum Size Subarray Sum](Problems/0209.cpp) |

| 0217 | Easy | [Contains Duplicate](Problems/0217.cpp) |

| 0222 | Medium | [Count Complete Tree Nodes](Problems/0222.cpp) | | 0223 | Medium | [Rectangle Area](Problems/0223.cpp) | | 0226 | Easy | [Invert Binary Tree](Problems/0226.cpp) | | 0234 | Easy | [Palindrome Linked List](Problems/0234.cpp) | | 0236 | Medium | [Lowest Common Ancestor of a Binary Tree](Problems/0236.cpp) | | 0237 | Medium | [Delete Node in a Linked List](Problems/0237.cpp) |

| 0238 | Medium | [Product of Array Except Self](Problems/0238.cpp) |

| 0242 | Easy | [Valid Anagram](Problems/0242.cpp) |

| 0257 | Easy | [Binary Tree Paths](Problems/0257.cpp) | | 0263 | Easy | [Ugly Number](Problems/0263.cpp) | | 0279 | Medium | [Perfect Squares](Problems/0279.cpp) | | 0283 | Easy | [Move Zeroes](Problems/0283.cpp) |

| 0287 | Medium | [Find the Duplicate Number](Problems/0287.cpp) |

| 0328 | Medium | [Odd Even Linked List](Problems/0328.cpp) | | 0338 | Easy | [Counting Bits](Problems/0338.cpp) | | 0344 | Easy | [Reverse String](Problems/0344.cpp) | | 0345 | Easy | [Reverse Vowels of a String](Problems/0345.cpp) |

| 0347 | Medium | [Top K Frequent Elements](Problems/0347.cpp) |

| 0374 | Easy | [Guess Number Higher or Lower](Problems/0374.cpp) | | 0383 | Easy | [Ransom Note](Problems/0383.cpp) | | 0387 | Easy | [First Unique Character in a String](Problems/0387.cpp) |

@@ -121,10 +133,12 @@ if you have any questions. | 0747 | Easy | [Largest Number At Least Twice of Others](Problems/0747.cpp) | | 0752 | Medium | [Open the Lock](Problems/0752.cpp) | | 0797 | Medium | [All Paths From Source to Target](Problems/0797.cpp) |

| 0802 | Medium | [Find Eventual Safe States](Problems/0802.cpp) |

| 0841 | Medium | [Keys and Rooms](Problems/0841.cpp) | | 0844 | Easy | [Backspace String Compare](Problems/0844.cpp) | | 0872 | Easy | [Leaf-Similar Trees](Problems/0872.cpp) | | 0876 | Easy | [Middle of the Linked List](Problems/0876.cpp) |

| 0886 | Medium | [Possible Bipartition](Problems/0886.cpp) |

| 0901 | Medium | [Online Stock Span](Problems/0901.cpp) | | 0905 | Easy | [Sort Array By Parity](Problems/0905.cpp) | | 0931 | Medium | [Minimum Falling Path Sum](Problems/0931.cpp) |

@@ -165,6 +179,7 @@ if you have any questions. | 1557 | Medium | [Minimum Number of Vertices to Reach All Nodes](Problems/1557.cpp) | | 1584 | Medium | [Min Cost to Connect All Points](Problems/1584.cpp) | | 1609 | Medium | [Even Odd Tree](Problems/1609.cpp) |

| 1615 | Medium | [Maximal Network Rank](Problems/1615.cpp) |

| 1646 | Easy | [Get Maximum in Generated Array](Problems/1646.cpp) | | 1669 | Medium | [Merge In Between Linked Lists](Problems/1669.cpp) | | 1672 | Easy | [Richest Customer Wealth](Problems/1672.cpp) |

@@ -186,6 +201,7 @@ if you have any questions. | 2285 | Medium | [Maximum Total Importance of Roads](Problems/2285.cpp) | | 2326 | Medium | [Spiral Matrix IV](Problems/2326.cpp) | | 2331 | Easy | [Evaluate Boolean Binary Tree](Problems/2331.cpp) |

| 2368 | Medium | [Reachable Nodes With Restrictions](Problems/2368.cpp) |

| 2390 | Medium | [Removing Stars From a String](Problems/2390.cpp) | | 2465 | Easy | [Number of Distinct Averages](Problems/2465.cpp) | | 2466 | Medium | [Count Ways To Build Good Strings](Problems/2466.cpp) |