Merge pull request #1047 from 0xff-dev/2577

Add solution and test-cases for problem 2577

leetcode/2501-2600/2577.Minimum-Time-to-Visit-a-Cell-In-a-Grid/README.md

@@ -0,0 +1,44 @@
+# [2577.Minimum Time to Visit a Cell In a Grid][title]
+
+## Description
+You are given a `m x n` matrix `grid` consisting of **non-negative** integers where `grid[row][col]` represents the **minimum** time required to be able to visit the cell `(row, col)`, which means you can visit the cell `(row, col)` only when the time you visit it is greater than or equal to `grid[row][col]`.
+
+You are standing in the **top-left** cell of the matrix in the `0th` second, and you must move to **any** adjacent cell in the four directions: up, down, left, and right. Each move you make takes 1 second.
+
+Return the **minimum** time required in which you can visit the bottom-right cell of the matrix. If you cannot visit the bottom-right cell, then return `-1`.
+
+**Example 1:**  
+
+![1](./1.png)
+
+```
+Input: grid = [[0,1,3,2],[5,1,2,5],[4,3,8,6]]
+Output: 7
+Explanation: One of the paths that we can take is the following:
+- at t = 0, we are on the cell (0,0).
+- at t = 1, we move to the cell (0,1). It is possible because grid[0][1] <= 1.
+- at t = 2, we move to the cell (1,1). It is possible because grid[1][1] <= 2.
+- at t = 3, we move to the cell (1,2). It is possible because grid[1][2] <= 3.
+- at t = 4, we move to the cell (1,1). It is possible because grid[1][1] <= 4.
+- at t = 5, we move to the cell (1,2). It is possible because grid[1][2] <= 5.
+- at t = 6, we move to the cell (1,3). It is possible because grid[1][3] <= 6.
+- at t = 7, we move to the cell (2,3). It is possible because grid[2][3] <= 7.
+The final time is 7. It can be shown that it is the minimum time possible.
+```
+
+**Example 2:**  
+
+![2](./2.png)
+
+```
+Input: grid = [[0,2,4],[3,2,1],[1,0,4]]
+Output: -1
+Explanation: There is no path from the top left to the bottom-right cell.
+```
+
+## 结语
+
+如果你同我一样热爱数据结构、算法、LeetCode，可以关注我 GitHub 上的 LeetCode 题解：[awesome-golang-algorithm][me]
+
+[title]: https://leetcode.com/problems/minimum-time-to-visit-a-cell-in-a-grid
+[me]: https://github.com/kylesliu/awesome-golang-algorithm

leetcode/2501-2600/2577.Minimum-Time-to-Visit-a-Cell-In-a-Grid/Solution.go

@@ -1,5 +1,69 @@
 package Solution
 
-func Solution(x bool) bool {
+import "container/heap"
+
+var dirs2577 = [][2]int{
+	{0, 1}, {1, 0}, {0, -1}, {-1, 0},
+}
+
+type heap2577 [][3]int
+
+func (h *heap2577) Len() int {
+	return len(*h)
+}
+
+func (h *heap2577) Swap(i, j int) {
+	(*h)[i], (*h)[j] = (*h)[j], (*h)[i]
+}
+
+func (h *heap2577) Less(i, j int) bool {
+	return (*h)[i][2] < (*h)[j][2]
+}
+
+func (h *heap2577) Push(x any) {
+	*h = append(*h, x.([3]int))
+}
+
+func (h *heap2577) Pop() any {
+	old := *h
+	l := len(old)
+	x := old[l-1]
+	*h = old[:l-1]
 	return x
 }
+
+func Solution(grid [][]int) int {
+	if grid[0][1] > 1 && grid[1][0] > 1 {
+		// 根本走不了
+		return -1
+	}
+	m, n := len(grid), len(grid[0])
+	visited := make(map[[2]int]int)
+	visited[[2]int{0, 0}] = 0
+	q := heap2577{{0, 0, 0}}
+
+	for q.Len() > 0 {
+		cur := heap.Pop(&q).([3]int)
+		if cur[0] == m-1 && cur[1] == n-1 {
+			return cur[2]
+		}
+		for _, dir := range dirs2577 {
+			nx, ny := cur[0]+dir[0], cur[1]+dir[1]
+			if nx >= 0 && nx < m && ny >= 0 && ny < n {
+				cost := cur[2] + 1 // 耗时比目前小，直接+1过去
+				if diff := grid[nx][ny] - cur[2]; diff >= 1 {
+					cost = grid[nx][ny]
+					if diff&1 == 0 {
+						cost++
+					}
+				}
+				if v, ok := visited[[2]int{nx, ny}]; !ok || v > cost {
+					heap.Push(&q, [3]int{nx, ny, cost})
+					visited[[2]int{nx, ny}] = cost
+				}
+			}
+		}
+	}
+
+	return -1
+}

leetcode/2501-2600/2577.Minimum-Time-to-Visit-a-Cell-In-a-Grid/Solution_test.go

@@ -10,12 +10,11 @@ func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
 		name   string
-		inputs bool
-		expect bool
+		inputs [][]int
+		expect int
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", [][]int{{0, 1, 3, 2}, {5, 1, 2, 5}, {4, 3, 8, 6}}, 7},
+		{"TestCase2", [][]int{{0, 2, 4}, {3, 2, 1}, {1, 0, 4}}, -1},
 	}
 
 	//	开始测试
@@ -30,10 +29,10 @@ func TestSolution(t *testing.T) {
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }