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feat: add solutions to lc problem: No.1970 (#3549)
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No.1970.Last Day Where You Can Still Cross
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@yanglbme
yanglbme committed Sep 21, 2024
1 parent 6f14f9b commit aed6166
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627 changes: 513 additions & 114 deletions solution/1900-1999/1970.Last Day Where You Can Still Cross/README.md
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627 changes: 513 additions & 114 deletions solution/1900-1999/1970.Last Day Where You Can Still Cross/README_EN.md
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70 changes: 39 additions & 31 deletions solution/1900-1999/1970.Last Day Where You Can Still Cross/Solution.cpp
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Original file line number Diff line number Diff line change
@@ -1,38 +1,46 @@
class Solution {
public:
vector<int> p;
int dirs[4][2] = {{0, -1}, {0, 1}, {1, 0}, {-1, 0}};
int row, col;

int latestDayToCross(int row, int col, vector<vector<int>>& cells) {
int n = row * col;
this->row = row;
this->col = col;
p.resize(n + 2);
for (int i = 0; i < p.size(); ++i) p[i] = i;
vector<vector<bool>> grid(row, vector<bool>(col, false));
int top = n, bottom = n + 1;
for (int k = cells.size() - 1; k >= 0; --k) {
int i = cells[k][0] - 1, j = cells[k][1] - 1;
grid[i][j] = true;
for (auto e : dirs) {
if (check(i + e[0], j + e[1], grid)) {
p[find(i * col + j)] = find((i + e[0]) * col + j + e[1]);
int l = 1, r = cells.size();
int g[row][col];
int dirs[5] = {0, 1, 0, -1, 0};
auto check = [&](int k) -> bool {
memset(g, 0, sizeof(g));
for (int i = 0; i < k; ++i) {
g[cells[i][0] - 1][cells[i][1] - 1] = 1;
}
queue<pair<int, int>> q;
for (int j = 0; j < col; ++j) {
if (g[0][j] == 0) {
q.emplace(0, j);
g[0][j] = 1;
}
}
while (!q.empty()) {
auto [x, y] = q.front();
q.pop();
if (x == row - 1) {
return true;
}
for (int i = 0; i < 4; ++i) {
int nx = x + dirs[i];
int ny = y + dirs[i + 1];
if (nx >= 0 && nx < row && ny >= 0 && ny < col && g[nx][ny] == 0) {
q.emplace(nx, ny);
g[nx][ny] = 1;
}
}
}
if (i == 0) p[find(i * col + j)] = find(top);
if (i == row - 1) p[find(i * col + j)] = find(bottom);
if (find(top) == find(bottom)) return k;
return false;
};
while (l < r) {
int mid = (l + r + 1) >> 1;
if (check(mid)) {
l = mid;
} else {
r = mid - 1;
}
}
return 0;
}

bool check(int i, int j, vector<vector<bool>>& grid) {
return i >= 0 && i < row && j >= 0 && j < col && grid[i][j];
}

int find(int x) {
if (p[x] != x) p[x] = find(p[x]);
return p[x];
return l;
}
};
};
75 changes: 37 additions & 38 deletions solution/1900-1999/1970.Last Day Where You Can Still Cross/Solution.go
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Original file line number Diff line number Diff line change
@@ -1,45 +1,44 @@
var p []int

func latestDayToCross(row int, col int, cells [][]int) int {
n := row * col
p = make([]int, n+2)
for i := 0; i < len(p); i++ {
p[i] = i
}
grid := make([][]bool, row)
for i := 0; i < row; i++ {
grid[i] = make([]bool, col)
}
top, bottom := n, n+1
dirs := [4][2]int{{0, -1}, {0, 1}, {1, 0}, {-1, 0}}
for k := len(cells) - 1; k >= 0; k-- {
i, j := cells[k][0]-1, cells[k][1]-1
grid[i][j] = true
for _, e := range dirs {
if check(i+e[0], j+e[1], grid) {
p[find(i*col+j)] = find((i+e[0])*col + j + e[1])
}
l, r := 1, len(cells)
dirs := [5]int{-1, 0, 1, 0, -1}
check := func(k int) bool {
g := make([][]int, row)
for i := range g {
g[i] = make([]int, col)
}
if i == 0 {
p[find(i*col+j)] = find(top)
for i := 0; i < k; i++ {
g[cells[i][0]-1][cells[i][1]-1] = 1
}
q := [][2]int{}
for j := 0; j < col; j++ {
if g[0][j] == 0 {
g[0][j] = 1
q = append(q, [2]int{0, j})
}
}
if i == row-1 {
p[find(i*col+j)] = find(bottom)
for len(q) > 0 {
x, y := q[0][0], q[0][1]
q = q[1:]
if x == row-1 {
return true
}
for i := 0; i < 4; i++ {
nx, ny := x+dirs[i], y+dirs[i+1]
if nx >= 0 && nx < row && ny >= 0 && ny < col && g[nx][ny] == 0 {
g[nx][ny] = 1
q = append(q, [2]int{nx, ny})
}
}
}
if find(top) == find(bottom) {
return k
return false
}
for l < r {
mid := (l + r + 1) >> 1
if check(mid) {
l = mid
} else {
r = mid - 1
}
}
return 0
return l
}

func check(i, j int, grid [][]bool) bool {
return i >= 0 && i < len(grid) && j >= 0 && j < len(grid[0]) && grid[i][j]
}

func find(x int) int {
if p[x] != x {
p[x] = find(p[x])
}
return p[x]
}
82 changes: 42 additions & 40 deletions solution/1900-1999/1970.Last Day Where You Can Still Cross/Solution.java
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Original file line number Diff line number Diff line change
@@ -1,49 +1,51 @@
class Solution {
private int[] p;
private int row;
private int col;
private boolean[][] grid;
private int[][] dirs = new int[][] {{0, -1}, {0, 1}, {1, 0}, {-1, 0}};
private int[][] cells;
private int m;
private int n;

public int latestDayToCross(int row, int col, int[][] cells) {
int n = row * col;
this.row = row;
this.col = col;
p = new int[n + 2];
for (int i = 0; i < p.length; ++i) {
p[i] = i;
}
grid = new boolean[row][col];
int top = n, bottom = n + 1;
for (int k = cells.length - 1; k >= 0; --k) {
int i = cells[k][0] - 1, j = cells[k][1] - 1;
grid[i][j] = true;
for (int[] e : dirs) {
if (check(i + e[0], j + e[1])) {
p[find(i * col + j)] = find((i + e[0]) * col + j + e[1]);
}
}
if (i == 0) {
p[find(i * col + j)] = find(top);
}
if (i == row - 1) {
p[find(i * col + j)] = find(bottom);
}
if (find(top) == find(bottom)) {
return k;
int l = 1, r = cells.length;
this.cells = cells;
this.m = row;
this.n = col;
while (l < r) {
int mid = (l + r + 1) >> 1;
if (check(mid)) {
l = mid;
} else {
r = mid - 1;
}
}
return 0;
return l;
}

private int find(int x) {
if (p[x] != x) {
p[x] = find(p[x]);
private boolean check(int k) {
int[][] g = new int[m][n];
for (int i = 0; i < k; i++) {
g[cells[i][0] - 1][cells[i][1] - 1] = 1;
}
return p[x];
}

private boolean check(int i, int j) {
return i >= 0 && i < row && j >= 0 && j < col && grid[i][j];
final int[] dirs = {-1, 0, 1, 0, -1};
Deque<int[]> q = new ArrayDeque<>();
for (int j = 0; j < n; j++) {
if (g[0][j] == 0) {
q.offer(new int[] {0, j});
g[0][j] = 1;
}
}
while (!q.isEmpty()) {
int[] p = q.poll();
int x = p[0], y = p[1];
if (x == m - 1) {
return true;
}
for (int i = 0; i < 4; i++) {
int nx = x + dirs[i], ny = y + dirs[i + 1];
if (nx >= 0 && nx < m && ny >= 0 && ny < n && g[nx][ny] == 0) {
q.offer(new int[] {nx, ny});
g[nx][ny] = 1;
}
}
}
return false;
}
}
}
49 changes: 24 additions & 25 deletions solution/1900-1999/1970.Last Day Where You Can Still Cross/Solution.py
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Original file line number Diff line number Diff line change
@@ -1,28 +1,27 @@
class Solution:
def latestDayToCross(self, row: int, col: int, cells: List[List[int]]) -> int:
n = row * col
p = list(range(n + 2))
grid = [[False] * col for _ in range(row)]
top, bottom = n, n + 1

def find(x):
if p[x] != x:
p[x] = find(p[x])
return p[x]
def check(k: int) -> bool:
g = [[0] * col for _ in range(row)]
for i, j in cells[:k]:
g[i - 1][j - 1] = 1
q = [(0, j) for j in range(col) if g[0][j] == 0]
for x, y in q:
if x == row - 1:
return True
for a, b in pairwise(dirs):
nx, ny = x + a, y + b
if 0 <= nx < row and 0 <= ny < col and g[nx][ny] == 0:
q.append((nx, ny))
g[nx][ny] = 1
return False

def check(i, j):
return 0 <= i < row and 0 <= j < col and grid[i][j]

for k in range(len(cells) - 1, -1, -1):
i, j = cells[k][0] - 1, cells[k][1] - 1
grid[i][j] = True
for x, y in [[0, 1], [0, -1], [1, 0], [-1, 0]]:
if check(i + x, j + y):
p[find(i * col + j)] = find((i + x) * col + j + y)
if i == 0:
p[find(i * col + j)] = find(top)
if i == row - 1:
p[find(i * col + j)] = find(bottom)
if find(top) == find(bottom):
return k
return 0
n = row * col
l, r = 1, n
dirs = (-1, 0, 1, 0, -1)
while l < r:
mid = (l + r + 1) >> 1
if check(mid):
l = mid
else:
r = mid - 1
return l
41 changes: 41 additions & 0 deletions solution/1900-1999/1970.Last Day Where You Can Still Cross/Solution.ts
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Original file line number Diff line number Diff line change
@@ -0,0 +1,41 @@
function latestDayToCross(row: number, col: number, cells: number[][]): number {
let [l, r] = [1, cells.length];
const check = (k: number): boolean => {
const g: number[][] = Array.from({ length: row }, () => Array(col).fill(0));
for (let i = 0; i < k; ++i) {
const [x, y] = cells[i];
g[x - 1][y - 1] = 1;
}
const q: number[][] = [];
for (let j = 0; j < col; ++j) {
if (g[0][j] === 0) {
q.push([0, j]);
g[0][j] = 1;
}
}
const dirs: number[] = [-1, 0, 1, 0, -1];
for (const [x, y] of q) {
if (x === row - 1) {
return true;
}
for (let i = 0; i < 4; ++i) {
const nx = x + dirs[i];
const ny = y + dirs[i + 1];
if (nx >= 0 && nx < row && ny >= 0 && ny < col && g[nx][ny] === 0) {
q.push([nx, ny]);
g[nx][ny] = 1;
}
}
}
return false;
};
while (l < r) {
const mid = (l + r + 1) >> 1;
if (check(mid)) {
l = mid;
} else {
r = mid - 1;
}
}
return l;
}
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