Add solution and test-cases for problem 1631

leetcode/1601-1700/1631.Path-With-Minimum-Effort/README.md

@@ -1,28 +1,42 @@
 # [1631.Path With Minimum Effort][title]
 
-> [!WARNING|style:flat]
-> This question is temporarily unanswered if you have good ideas. Welcome to [Create Pull Request PR](https://github.com/kylesliu/awesome-golang-algorithm)
-
 ## Description
+You are a hiker preparing for an upcoming hike. You are given `heights`, a 2D array of size `rows x columns`, where `heights[row][col]` represents the height of cell (`row, col`). You are situated in the top-left cell, (`0, 0`), and you hope to travel to the bottom-right cell, (`rows-1, columns-1`) (i.e., **0-indexed**). You can move **up**, **down**, **left**, or **right**, and you wish to find a route that requires the minimum **effort**.
+
+A route's **effort** is the **maximum absolute difference** in heights between two consecutive cells of the route.
+
+Return the minimum **effort** required to travel from the top-left cell to the bottom-right cell.
 
-**Example 1:**
+**Example 1:**  
+
+![example1](./ex1.png)
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: heights = [[1,2,2],[3,8,2],[5,3,5]]
+Output: 2
+Explanation: The route of [1,3,5,3,5] has a maximum absolute difference of 2 in consecutive cells.
+This is better than the route of [1,2,2,2,5], where the maximum absolute difference is 3.
 ```
 
-## 题意
-> ...
+**Example 2:**  
 
-## 题解
+![example2](./ex2.png)
 
-### 思路1
-> ...
-Path With Minimum Effort
-```go
+```
+Input: heights = [[1,2,3],[3,8,4],[5,3,5]]
+Output: 1
+Explanation: The route of [1,2,3,4,5] has a maximum absolute difference of 1 in consecutive cells, which is better than route [1,3,5,3,5].
 ```
 
+**Example 3:**  
+
+![example3](./ex3.png)
+
+```
+Input: heights = [[1,2,1,1,1],[1,2,1,2,1],[1,2,1,2,1],[1,2,1,2,1],[1,1,1,2,1]]
+Output: 0
+Explanation: This route does not require any effort.
+```
 
 ## 结语
 

leetcode/1601-1700/1631.Path-With-Minimum-Effort/Solution.go

@@ -1,5 +1,53 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+func Solution(heights [][]int) int {
+	// binary search + bfs
+	var (
+		left  = 0
+		right = 1000000
+		bfs   func(int, int, int) bool
+		dirs  = [][]int{{0, 1}, {0, -1}, {1, 0}, {-1, 0}}
+	)
+
+	rows, cols := len(heights), len(heights[0])
+	bfs = func(x, y, limit int) bool {
+		visited := [100][100]bool{}
+		queue := [][]int{{x, y}}
+		visited[x][y] = true
+		for len(queue) > 0 {
+			next := make([][]int, 0)
+			for _, item := range queue {
+				if item[0] == rows-1 && item[1] == cols-1 {
+					return true
+				}
+				for _, dir := range dirs {
+					nx, ny := item[0]+dir[0], item[1]+dir[1]
+					if nx < 0 || nx >= rows || ny < 0 || ny >= cols || visited[nx][ny] {
+						continue
+					}
+					diff := heights[nx][ny] - heights[item[0]][item[1]]
+					if diff < 0 {
+						diff = ^diff + 1
+					}
+					if diff > limit {
+						continue
+					}
+					next = append(next, []int{nx, ny})
+					visited[nx][ny] = true
+				}
+			}
+			queue = next
+		}
+		return false
+	}
+	for left < right {
+		m := left + (right-left)/2
+		if bfs(0, 0, m) {
+			right = m
+			continue
+		}
+		left = m + 1
+	}
+
+	return left
 }

leetcode/1601-1700/1631.Path-With-Minimum-Effort/Solution_test.go

@@ -10,12 +10,12 @@ 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{{1, 2, 2}, {3, 8, 2}, {5, 3, 5}}, 2},
+		{"TestCase2", [][]int{{1, 2, 3}, {3, 8, 4}, {5, 3, 5}}, 1},
+		{"TestCase3", [][]int{{1, 2, 1, 1, 1}, {1, 2, 1, 2, 1}, {1, 2, 1, 2, 1}, {1, 2, 1, 2, 1}, {1, 1, 1, 2, 1}}, 0},
 	}
 
 	//	开始测试
@@ -30,10 +30,10 @@ 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() {
 }