leetcode

Algorithm II: Day 11

4 files changed, 93 insertions(+), 1 deletions(-)

diff --git a/ Problems/0017.cpp b/ Problems/0017.cpp

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

class Solution {

public:

vector<string> letterCombinations(string digits) {

vector<string> um = {"abc", "def", "ghi", "jkl",

"mno", "pqrs", "tuv", "wxyz"},

res = {""};

for (char d : digits) {

vector<string> tmp;

for (char l : um[d - '2'])

for (const string &s : res) tmp.push_back(s + l);

res = tmp;

}

return res.size() > 1 ? res : vector<string>();

}

};

diff --git a/ Problems/0079.cpp b/ Problems/0079.cpp

@@ -0,0 +1,45 @@

class Solution {

typedef vector<vector<char>> Matrix;

typedef vector<vector<bool>> Marked;

const vector<pair<int, int>> offsets = {

{ 0, 1},

{ 0, -1},

{ 1, 0},

{-1, 0}

};

int n, m;

int valid(int x, int y) { return x >= 0 && x < n && y >= 0 && y < m; }

string word;

bool dfs(const Matrix &mat, Marked &mark, int a, int b, int got) {

if (got == word.size()) return true;

mark[a][b] = true;

for (auto [oa, ob] : offsets) {

int x = a + oa, y = b + ob;

if (!valid(x, y) || mark[x][y] || mat[x][y] != word[got]) continue;

if (dfs(mat, mark, x, y, got + 1)) return true;

}

mark[a][b] = false;

return false;

}

public:

bool exist(const Matrix &board, string word) {

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

this->word = word;

Marked visited(n, vector<bool>(m, false));

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

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

if (board[i][j] != word[0]) continue;

if (dfs(board, visited, i, j, 1)) return true;

}

}

return false;

}

};

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

@@ -17,7 +17,8 @@ for solving problems. * [MST from edge priority queue](Templates/MST_pq.cpp) * [MST from edge vector](Templates/MST_vector.cpp)

* [Matrix BFS/Flood fill](Templates/bfs_floodfill.cpp)

* [Matrix BFS/Flood fill Iterative](Templates/bfs_floodfill.cpp)

* [Matrix BFS/Flood fill Recursive](Templates/bfs_floodfill_recursive.cpp)

* [Union Find](Templates/Union_Find.cpp) ## Problems

@@ -34,6 +35,7 @@ for solving problems. | 0013 | Easy | [Roman to Integer](Problems/0013.cpp) | | 0014 | Easy | [Longest Common Prefix](Problems/0014.cpp) | | 0015 | Medium | [3Sum](Problems/0015.cpp) |

| 0017 | Medium | [Letter Combinations of a Phone Number](Problems/0017.cpp) |

| 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) |

@@ -75,6 +77,7 @@ for solving problems. | 0075 | Medium | [Sort Colors](Problems/0075.cpp) | | 0077 | Medium | [Combinations](Problems/0077.cpp) | | 0078 | Medium | [Subsets](Problems/0078.cpp) |

| 0079 | Medium | [Word Search](Problems/0079.cpp) |

| 0082 | Medium | [Remove Duplicates from Sorted List II](Problems/0082.cpp) | | 0083 | Easy | [Remove Duplicates from Sorted List](Problems/0083.cpp) | | 0084 | Hard | [Largest Rectangle in Histogram](Problems/0084.cpp) |

diff --git a/ Templates/bfs_floodfill_recursive.cpp b/ Templates/bfs_floodfill_recursive.cpp

@@ -0,0 +1,27 @@

// Matrix BFS/Flood fill Recursive

typedef vector<vector<int>> Matrix;

typedef vector<vector<bool>> Marked;

const vector<pair<int, int>> offsets = {

{ 0, 1},

{ 0, -1},

{ 1, 0},

{-1, 0}

};

int n, m;

int valid(int x, int y) { return x >= 0 && x < n && y >= 0 && y < m; }

bool dfs(const Matrix &mat, Marked &mark, int a, int b) {

if (got == word.size()) return true;

mark[a][b] = true;

for (auto [oa, ob] : offsets) {

int x = a + oa, y = b + ob;

if (!valid(x, y) || mark[x][y]) continue;

if (dfs(mat, mark, x, y)) return true;

}

mark[a][b] = false;

return false;

}