leetcode

Some daily problems

4 files changed, 109 insertions(+), 22 deletions(-)

diff --git a/ Problems/0290.cpp b/ Problems/0290.cpp

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

class Solution {

public:

bool wordPattern(string pattern, string s) {

vector<string> done(26, "");

unordered_set<string> st;

int c = 0;

istringstream in(s);

for (string crnt; in >> crnt; ++c) {

if (c >= pattern.size()) return false;

int index = pattern[c] - 'a';

if (done[index].empty()) {

if (st.count(crnt)) return false;

st.insert(done[index] = crnt);

} else if (done[index] != crnt)

return false;

}

if (pattern.size() > c) return false;

return true;

}

};

diff --git a/ Problems/0494.cpp b/ Problems/0494.cpp

@@ -1,30 +1,37 @@

// Initial solution

class Solution { public: int findTargetSumWays(vector<int> &nums, int target) {

queue<int> st;

st.push(0);

int zc = 0;

for (int i = 0; i != nums.size(); ++i) {

if (!nums[i]) {

zc++;

continue;

}

for (int j = st.size(); j > 0; --j) {

int n = st.front();

st.pop();

st.push(n - nums[i]);

st.push(n + nums[i]);

unordered_map<int, int> crnt;

crnt[0] = 1;

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

unordered_map<int, int> next;

for (auto &p : crnt) {

next[p.first + nums[i]] += p.second;

next[p.first - nums[i]] += p.second;

}

crnt = next;

}

return crnt[target];

}

};

int count = 0;

while (!st.empty()) {

if (st.front() == target) count++;

st.pop();

// Optimized using array;

class Solution {

public:

int findTargetSumWays(vector<int> &nums, int target) {

int total = accumulate(nums.begin(), nums.end(), 0);

vector<int> dp(2 * total + 1);

dp[total] = 1;

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

vector<int> next(2 * total + 1);

for (int j = 0; j < dp.size(); j++) {

if (!dp[j]) continue;

next[j + nums[i]] += dp[j];

next[j - nums[i]] += dp[j];

}

dp = next;

}

return count * exp2(zc);

return abs(target) > total ? 0 : dp[target + total];

} };

diff --git a/ Problems/0980.cpp b/ Problems/0980.cpp

@@ -0,0 +1,56 @@

class Solution {

vector<pair<int, int>> offset = {

{ 0, 1},

{ 0, -1},

{ 1, 0},

{-1, 0}

};

int m, n;

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

int find(vector<vector<int>> &grid, int x, int y, int obs) {

stack<pair<int, int>> st;

st.push({x, y});

int count = 0, goal = m * n - obs - 1, crnt = 0;

while (!st.empty()) {

auto p = st.top();

if (grid[p.first][p.second] == 3) {

st.pop();

grid[p.first][p.second] = 0;

crnt--;

continue;

}

grid[p.first][p.second] = 3;

crnt++;

for (auto &o : offset) {

int x = p.first + o.first;

int y = p.second + o.second;

if (!valid(x, y) || grid[x][y] == 3 || grid[x][y] == -1) continue;

if (grid[x][y] == 2)

count += crnt == goal;

else

st.push({x, y});

}

}

return count;

}

public:

int uniquePathsIII(vector<vector<int>> &grid) {

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

int x, y, count = 0;

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

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

if (grid[i][j] == 1)

x = i, y = j;

else if (grid[i][j] == -1)

count++;

return find(grid, x, y, count);

}

};

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

@@ -93,6 +93,7 @@ if you have any questions. | 0279 | Medium | [Perfect Squares](Problems/0279.cpp) | | 0283 | Easy | [Move Zeroes](Problems/0283.cpp) | | 0287 | Medium | [Find the Duplicate Number](Problems/0287.cpp) |

| 0290 | Easy | [Word Pattern](Problems/0290.cpp) |

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

@@ -114,6 +115,7 @@ if you have any questions. | 0448 | Easy | [Find All Numbers Disappeared in an Array](Problems/0448.cpp) | | 0450 | Medium | [Delete Node in a BST](Problems/0450.cpp) | | 0485 | Easy | [Max Consecutive Ones](Problems/0485.cpp) |

| 0494 | Medium | [Target Sum](Problems/0494.cpp) |

| 0496 | Medium | [Next Greater Element I](Problems/0496.cpp) | | 0498 | Medium | [Diagonal Traverse](Problems/0498.cpp) | | 0501 | Easy | [Find Mode in Binary Search Tree](Problems/0501.cpp) |

@@ -167,6 +169,7 @@ if you have any questions. | 0959 | Medium | [Regions Cut By Slashes](Problems/0959.cpp) | | 0965 | Easy | [Univalued Binary Tree](Problems/0965.cpp) | | 0977 | Easy | [Squares of a Sorted Array](Problems/0977.cpp) |

| 0980 | Hard | [Unique Paths III](Problems/0980.cpp) |

| 0989 | Easy | [Add to Array-Form of Integer](Problems/0989.cpp) | | 0993 | Easy | [Cousins in Binary Tree](Problems/0993.cpp) | | 0997 | Easy | [Find the Town Judge](Problems/0997.cpp) |

@@ -237,7 +240,6 @@ if you have any questions. | Number | Difficulty | Solution | |:------:|:----------:|-------------------------------------------------------------------------------------------------|

| 0494 | Medium | [Target Sum](Problems/0494.cpp) |

| 0402 | Medium | [Remove K Digits](Problems/0402.cpp) | | 0129 | Medium | [Sum Root to Leaf Numbers](Problems/0129.cpp) | | 0542 | Medium | [01 Matrix](Problems/0542.cpp) |