leetcode

5 Random Problems

6 files changed, 202 insertions(+), 0 deletions(-)

diff --git a/ Problems/0454.cpp b/ Problems/0454.cpp

@@ -0,0 +1,23 @@

class Solution {

public:

int fourSumCount(const vector<int> &nums1, const vector<int> &nums2, const vector<int> &nums3,

const vector<int> &nums4) const {

const int n = size(nums1);

unordered_map<int, int> um;

int res = 0;

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

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

um[nums1[i] + nums2[j]]++;

}

}

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

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

res += um[-(nums3[i] + nums4[j])];

}

}

return res;

}

};

diff --git a/ Problems/0641.cpp b/ Problems/0641.cpp

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

class MyCircularDeque {

const int n;

vector<int> q;

int size = 0;

int head = 0, tail = 0;

public:

MyCircularDeque(int k) : n(k), q(k) {}

bool insertFront(int value) {

if (size == n) return false;

q[head] = value;

head = (head + 1) % n;

size++;

return true;

}

bool insertLast(int value) {

if (size == n) return false;

tail = (tail - 1 + n) % n;

q[tail] = value;

size++;

return true;

}

bool deleteFront() {

if (!size) return false;

head = (head - 1 + n) % n;

size--;

return true;

}

bool deleteLast() {

if (!size) return false;

tail = (tail + 1) % n;

size--;

return true;

}

int getFront() const { return size ? q[(head - 1 + n) % n] : -1; }

int getRear() const { return size ? q[tail] : -1; }

bool isEmpty() const { return size == 0; }

bool isFull() const { return size == n; }

};

diff --git a/ Problems/0677.cpp b/ Problems/0677.cpp

@@ -0,0 +1,82 @@

// Only Trie

class MapSum {

struct Node {

Node(){};

Node *children[27] = {nullptr};

int &value = reinterpret_cast<int &>(children[0]);

int trail = 0;

};

Node *trie = new Node();

public:

void insert(const string &key, int val) {

Node *prev = trie;

for (const char c : key) {

const int idx = c & 0x1F;

if (!prev->children[idx]) {

prev = nullptr;

break;

};

prev = prev->children[idx];

}

const int diff = prev ? val - prev->value : val;

Node *crnt = trie;

for (const char c : key) {

const int idx = c & 0x1F;

crnt->trail += diff;

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

crnt = crnt->children[idx];

}

crnt->value = val;

}

int sum(const string &prefix) const {

const Node *crnt = trie;

for (const char c : prefix) {

const int idx = c & 0x1F;

if (!crnt->children[idx]) return 0;

crnt = crnt->children[idx];

}

return crnt->value + crnt->trail;

}

};

// Trie + hash map

class MapSum {

struct Node {

Node(){};

Node *children[27] = {nullptr};

int &value = reinterpret_cast<int &>(children[0]);

};

Node *trie = new Node();

unordered_map<string, int> um;

public:

void insert(const string &key, int val) {

const int diff = val - um[key];

Node *crnt = trie;

for (const char c : key) {

const int idx = c & 0x1F;

crnt->value += diff;

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

crnt = crnt->children[idx];

}

crnt->value += diff;

um[key] = val;

}

int sum(const string &prefix) const {

const Node *crnt = trie;

for (const char c : prefix) {

const int idx = c & 0x1F;

if (!crnt->children[idx]) return 0;

crnt = crnt->children[idx];

}

return crnt->value;

}

};

diff --git a/ Problems/1690.cpp b/ Problems/1690.cpp

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

class Solution {

static int dp[1001][1001];

static int solve(const vector<int> &stones, int i, int j, int sum) {

if (i > j) return 0;

if (dp[i][j] != -1) return dp[i][j];

const int a = sum - stones[i] - solve(stones, i + 1, j, sum - stones[i]);

const int b = sum - stones[j] - solve(stones, i, j - 1, sum - stones[j]);

return dp[i][j] = max(a, b);

}

public:

Solution() { memset(dp, 0xFF, sizeof(dp)); }

int stoneGameVII(const vector<int> &stones) const {

const int sum = accumulate(begin(stones), end(stones), 0);

return solve(stones, 0, size(stones) - 1, sum);

}

};

int Solution::dp[1001][1001];

diff --git a/ Problems/2596.cpp b/ Problems/2596.cpp

@@ -0,0 +1,25 @@

class Solution {

public:

bool checkValidGrid(const vector<vector<int>> &grid) const {

static const int offset_x[] = {-2, -2, -1, -1, 1, 1, 2, 2};

static const int offset_y[] = {-1, 1, -2, 2, -2, 2, -1, 1};

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

int x = 0, y = 0;

if (grid[0][0] != 0) return false;

for (int cnt = 1; cnt < n * m; cnt++) {

for (int k = 0; k < 8; k++) {

const int a = x + offset_x[k];

const int b = y + offset_y[k];

if (a < 0 || b < 0 || a >= n || b >= m) continue;

if (grid[a][b] == cnt) {

x = a, y = b;

goto next;

}

}

return false;

next:;

}

return true;

}

};

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

@@ -330,6 +330,7 @@ for solving problems. | 0450 | Medium | [Delete Node in a BST](Problems/0450.cpp) | | 0451 | Medium | [Sort Characters By Frequency](Problems/0451.cpp) | | 0452 | Medium | [Minimum Number of Arrows to Burst Balloons](Problems/0452.cpp) |

| 0454 | Medium | [4Sum II](Problems/0454.cpp) |

| 0455 | Easy | [Assign Cookies](Problems/0455.cpp) | | 0456 | Medium | [132 Pattern](Problems/0456.cpp) | | 0458 | Hard | [Poor Pigs](Problems/0458.cpp) |

@@ -403,6 +404,7 @@ for solving problems. | 0627 | Easy | [Swap Salary](Problems/0627.cpp) | | 0636 | Medium | [Exclusive Time of Functions](Problems/0636.cpp) | | 0637 | Easy | [Average of Levels in Binary Tree](Problems/0637.cpp) |

| 0641 | Medium | [Design Circular Deque](Problems/0641.cpp) |

| 0643 | Easy | [Maximum Average Subarray I](Problems/0643.cpp) | | 0646 | Medium | [Maximum Length of Pair Chain](Problems/0646.cpp) | | 0647 | Medium | [Palindromic Substrings](Problems/0647.cpp) |

@@ -420,6 +422,7 @@ for solving problems. | 0671 | Easy | [Second Minimum Node In a Binary Tree](Problems/0671.cpp) | | 0673 | Medium | [Number of Longest Increasing Subsequence](Problems/0673.cpp) | | 0676 | Medium | [Implement Magic Dictionary](Problems/0676.cpp) |

| 0677 | Medium | [Map Sum Pairs](Problems/0677.cpp) |

| 0684 | Medium | [Redundant Connection](Problems/0684.cpp) | | 0688 | Medium | [Knight Probability in Chessboard](Problems/0688.cpp) | | 0690 | Medium | [Employee Importance](Problems/0690.cpp) |

@@ -819,6 +822,7 @@ for solving problems. | 1685 | Medium | [Sum of Absolute Differences in a Sorted Array](Problems/1685.cpp) | | 1688 | Easy | [Count of Matches in Tournament](Problems/1688.cpp) | | 1689 | Medium | [Partitioning Into Minimum Number Of Deci-Binary Numbers](Problems/1689.cpp) |

| 1690 | Medium | [Stone Game VII](Problems/1690.cpp) |

| 1693 | Easy | [Daily Leads and Partners](Problems/1693.cpp) | | 1695 | Medium | [Maximum Erasure Value](Problems/1695.cpp) | | 1696 | Medium | [Jump Game VI](Problems/1696.cpp) |

@@ -1030,6 +1034,7 @@ for solving problems. | 2568 | Medium | [Minimum Impossible OR](Problems/2568.cpp) | | 2579 | Medium | [Count Total Number of Colored Cells](Problems/2579.cpp) | | 2592 | Medium | [Maximize Greatness of an Array](Problems/2592.cpp) |

| 2596 | Medium | [Check Knight Tour Configuration](Problems/2596.cpp) |

| 2610 | Medium | [Convert an Array Into a 2D Array With Conditions](Problems/2610.cpp) | | 2616 | Medium | [Minimize the Maximum Difference of Pairs](Problems/2616.cpp) | | 2620 | Easy | [Counter](Problems/2620.js) |