leetcode

Daily Problem

2 files changed, 62 insertions(+), 1 deletions(-)

diff --git a/ Problems/1970.cpp b/ Problems/1970.cpp

@@ -0,0 +1,60 @@

class UnionFind {

int root[20002], size[20002];

public:

UnionFind() {

for (int i = 0; i < 20002; i++) {

root[i] = i;

size[i] = 1;

}

}

int find(int x) {

while (x != root[x]) x = root[x] = root[root[x]];

return x;

}

void join(int x, int y) {

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

if (x != y) {

if (size[x] > size[y]) swap(x, y);

root[x] = y;

size[y] += size[x];

}

}

bool connected(int x, int y) { return find(x) == find(y); }

};

class Solution {

int grid[20000] = {0};

public:

int latestDayToCross(int row, int col, const vector<vector<int>> &cells) {

static const auto index = [&](int i, int j) { return i * col + j; };

static const auto valid = [&](int i, int j) {

return i >= 0 && j >= 0 && i < row && j < col;

};

static const int offset_x[] = {0, 0, 1, -1};

static const int offset_y[] = {1, -1, 0, 0};

UnionFind uf;

for (int i = cells.size() - 1; i >= 0; i--) {

const int x = cells[i][0] - 1, y = cells[i][1] - 1, ind = index(x, y);

grid[ind] = true;

for (int k = 0; k < 4; k++) {

int i = x + offset_x[k], j = y + offset_y[k];

if (!valid(i, j) || !grid[index(i, j)]) continue;

uf.join(ind, index(i, j));

}

if (x == 0) uf.join(ind, 20000);

if (x == row - 1) uf.join(ind, 20001);

if (uf.connected(20000, 20001)) return i;

}

return row * col;

}

};

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

@@ -360,7 +360,7 @@ for solving problems. | 0844 | Easy | [Backspace String Compare](Problems/0844.cpp) | | 0851 | Medium | [Loud and Rich](Problems/0851.cpp) | | 0853 | Medium | [Car Fleet](Problems/0853.cpp) |

| 0864 | Medium | [Shortest Path to Get All Keys](Problems/0864.cpp) |

| 0864 | Hard | [Shortest Path to Get All Keys](Problems/0864.cpp) |

| 0872 | Easy | [Leaf-Similar Trees](Problems/0872.cpp) | | 0875 | Medium | [Koko Eating Bananas](Problems/0875.cpp) | | 0876 | Easy | [Middle of the Linked List](Problems/0876.cpp) |

@@ -522,6 +522,7 @@ for solving problems. | 1926 | Medium | [Nearest Exit from Entrance in Maze](Problems/1926.cpp) | | 1962 | Medium | [Remove Stones to Minimize the Total](Problems/1962.cpp) | | 1964 | Hard | [Find the Longest Valid Obstacle Course at Each Position](Problems/1964.cpp) |

| 1970 | Hard | [Last Day Where You Can Still Cross](Problems/1970.cpp) |

| 1971 | Easy | [Find if Path Exists in Graph](Problems/1971.cpp) | | 1976 | Medium | [Number of Ways to Arrive at Destination](Problems/1976.cpp) | | 1991 | Easy | [Find the Middle Index in Array](Problems/1991.cpp) |