leetcode

Daily Problem and 2 Random Problems

4 files changed, 174 insertions(+), 0 deletions(-)

diff --git a/ Problems/0127.cpp b/ Problems/0127.cpp

@@ -0,0 +1,91 @@

// Make graph and search, interesting similarity test, O(n^2)

class Solution {

static uint64_t convert(const string &word) {

uint64_t res = 0;

for (const char c : word)

res = (res << 5) + (c & 0x1F);

return res;

}

static bool connected(uint64_t a, uint64_t b) {

const uint64_t cmp = max(a, b) ^ min(a, b);

return (63 - __builtin_clzll(cmp)) / 5 == __builtin_ctzll(cmp) / 5;

}

public:

int ladderLength(const string &beginWord, const string &endWord, const vector<string> &wordList) const {

static uint64_t val[5001];

const int n = wordList.size();

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

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

val[i] = convert(wordList[i]);

val[n] = convert(beginWord);

int m = -1;

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

if (wordList[i] == beginWord) continue;

if (wordList[i] == endWord) m = i;

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

if (connected(val[i], val[j])) {

adj[i].push_back(j);

adj[j].push_back(i);

}

}

}

if (m == -1) return 0;

unordered_set<int> seen;

queue<int> q;

q.push(n);

seen.insert(n);

for (int lvl = 1; !q.empty(); lvl++) {

for (int k = q.size(); k > 0; k--) {

const int crnt = q.front();

q.pop();

for (const int next : adj[crnt]) {

if (seen.count(next)) continue;

if (next == m) return lvl + 1;

seen.insert(next);

q.push(next);

}

}

}

return 0;

}

};

// Optimal solution, by trying all similar strings, O(m*n)

class Solution {

public:

int ladderLength(const string &beginWord, const string &endWord, const vector<string> &wordList) const {

const int n = wordList.size(), m = wordList[0].size();

unordered_set<string> list(begin(wordList), end(wordList));

unordered_set<string> seen;

queue<string> q;

q.push(beginWord);

seen.insert(beginWord);

for (int lvl = 1; !q.empty(); lvl++) {

for (int k = q.size(); k > 0; k--) {

const string &crnt = q.front();

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

for (int c = 'a'; c <= 'z'; c++) {

string next = crnt;

next[i] = c;

if (list.count(next) && !seen.count(next)) {

if (next == endWord) return lvl + 1;

seen.insert(next);

q.push(next);

}

}

}

q.pop();

}

}

return 0;

}

};

diff --git a/ Problems/0212.cpp b/ Problems/0212.cpp

@@ -0,0 +1,58 @@

class Solution {

struct Node {

Node(){};

Node *children[27] = {nullptr};

bool &terminate = reinterpret_cast<bool &>(children[0]);

void insert(const string &s) {

Node *crnt = this;

for (const char c : s) {

const int idx = c & 0x1F;

if (!crnt->children[idx]) crnt->children[idx] = new Node();

crnt = crnt->children[idx];

}

crnt->terminate = true;

}

};

int n, m;

vector<string> res;

void dfs(vector<vector<char>> &board, Node *trie, int x, int y) {

const char c = board[x][y], idx = c & 0x1F;

if (c == '#' || !(trie = trie->children[idx])) return;

res.back().push_back(c);

if (trie->terminate) {

res.push_back(res.back());

trie->terminate = false;

}

board[x][y] = '#';

if (x > 0) dfs(board, trie, x - 1, y);

if (y > 0) dfs(board, trie, x, y - 1);

if (x < n) dfs(board, trie, x + 1, y);

if (y < m) dfs(board, trie, x, y + 1);

board[x][y] = c;

res.back().pop_back();

}

public:

vector<string> findWords(vector<vector<char>> &board, const vector<string> &words) {

Node *trie = new Node();

for (const string &word : words)

trie->insert(word);

n = board.size() - 1, m = board[0].size() - 1;

res.push_back("");

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

for (int j = 0; j <= m; j++) {

dfs(board, trie, i, j);

}

}

res.pop_back();

return res;

}

};

diff --git a/ Problems/1913.cpp b/ Problems/1913.cpp

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

class Solution {

public:

int maxProductDifference(vector<int> &nums) const {

sort(begin(nums), begin(nums) + 4);

int a = nums[0], b = nums[1];

int c = nums[2], d = nums[3];

for (int i = 4; i < nums.size(); i++) {

if (nums[i] > d) {

c = d;

d = nums[i];

} else if (nums[i] > c) {

c = nums[i];

} else if (nums[i] < a) {

b = a;

a = nums[i];

} else if (nums[i] < b) {

b = nums[i];

}

}

return c * d - a * b;

}

};

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

@@ -144,6 +144,7 @@ for solving problems. | 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) |

| 0127 | Hard | [Word Ladder](Problems/0127.cpp) |

| 0128 | Medium | [Longest Consecutive Sequence](Problems/0128.cpp) | | 0129 | Medium | [Sum Root to Leaf Numbers](Problems/0129.cpp) | | 0130 | Medium | [Surrounded Regions](Problems/0130.cpp) |

@@ -212,6 +213,7 @@ for solving problems. | 0209 | Medium | [Minimum Size Subarray Sum](Problems/0209.cpp) | | 0210 | Medium | [Course Schedule II](Problems/0210.cpp) | | 0211 | Medium | [Design Add and Search Words Data Structure](Problems/0211.cpp) |

| 0212 | Hard | [Word Search II](Problems/0212.cpp) |

| 0213 | Medium | [House Robber II](Problems/0213.cpp) | | 0215 | Medium | [Kth Largest Element in an Array](Problems/0215.cpp) | | 0216 | Medium | [Combination Sum III](Problems/0216.cpp) |

@@ -851,6 +853,7 @@ for solving problems. | 1905 | Medium | [Count Sub Islands](Problems/1905.cpp) | | 1907 | Medium | [Count Salary Categories](Problems/1907.cpp) | | 1910 | Medium | [Remove All Occurrences of a Substring](Problems/1910.cpp) |

| 1913 | Medium | [Maximum Product Difference Between Two Pairs](Problems/1913.cpp) |

| 1921 | Medium | [Eliminate Maximum Number of Monsters](Problems/1921.cpp) | | 1926 | Medium | [Nearest Exit from Entrance in Maze](Problems/1926.cpp) | | 1930 | Medium | [Unique Length-3 Palindromic Subsequences](Problems/1930.cpp) |