From 6a518a6f0b1ee1a3f5f5e140c8c091693b03b1e5 Mon Sep 17 00:00:00 2001 From: ziyun Date: Sat, 22 Jun 2019 18:37:25 +0800 Subject: [PATCH 1/2] update --- Week_03/id_39/LeetCode_102_39.js | 46 ++++++++++++++ Week_03/id_39/LeetCode_103_39.js | 50 +++++++++++++++ Week_03/id_39/LeetCode_107_39.js | 41 +++++++++++++ Week_03/id_39/LeetCode_200_39.js | 101 +++++++++++++++++++++++++++++++ Week_03/id_39/LeetCode_429_39.js | 43 +++++++++++++ Week_03/id_39/LeetCode_529_39.js | 37 +++++++++++ Week_03/id_39/NOTE.md | 13 ++++ 7 files changed, 331 insertions(+) create mode 100644 Week_03/id_39/LeetCode_102_39.js create mode 100644 Week_03/id_39/LeetCode_103_39.js create mode 100644 Week_03/id_39/LeetCode_107_39.js create mode 100644 Week_03/id_39/LeetCode_200_39.js create mode 100644 Week_03/id_39/LeetCode_429_39.js create mode 100644 Week_03/id_39/LeetCode_529_39.js diff --git a/Week_03/id_39/LeetCode_102_39.js b/Week_03/id_39/LeetCode_102_39.js new file mode 100644 index 00000000..620300a1 --- /dev/null +++ b/Week_03/id_39/LeetCode_102_39.js @@ -0,0 +1,46 @@ +/** + * Definition for a binary tree node. + * function TreeNode(val) { + * this.val = val; + * this.left = this.right = null; + * } + */ +/** + * @param {TreeNode} root + * @return {number[][]} + * https://leetcode.com/problems/binary-tree-level-order-traversal/ + */ +var levelOrder = function(root) { + if (!root) { + return []; + } + let result = []; + let level = [root]; + let queue = []; + let depth = -1; + + while (level.length) { + result[++depth] = []; + + while (level.length) { + let node = level.shift(); + + if (node.val != null) { + result[depth].push(node.val); + } + + + if (node.left) { + queue.push(node.left); + } + if (node.right) { + queue.push(node.right); + } + } + + level = queue; + queue = []; + } + + return result; +}; \ No newline at end of file diff --git a/Week_03/id_39/LeetCode_103_39.js b/Week_03/id_39/LeetCode_103_39.js new file mode 100644 index 00000000..c1bcc201 --- /dev/null +++ b/Week_03/id_39/LeetCode_103_39.js @@ -0,0 +1,50 @@ +/** + * Definition for a binary tree node. + * function TreeNode(val) { + * this.val = val; + * this.left = this.right = null; + * } + */ +/** + * @param {TreeNode} root + * @return {number[][]} + * https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/ + */ +var zigzagLevelOrder = function(root) { + if (!root) { + return []; + } + let queue = [root]; + let isOdd = true; + let levelNum = 1; + let result = []; + + while (queue.length) { + result.push([]); + let level = result.length - 1; + let count = 0; + while (levelNum) { + levelNum--; + let node = queue.shift(); + if (node.val != null) { + if (isOdd) { + result[level].push(node.val); + } else { + result[level].unshift(node.val); + } + } + if (node.left) { + queue.push(node.left); + count++; + } + if (node.right) { + queue.push(node.right); + count++; + } + } + levelNum = count; + isOdd = !isOdd; + } + + return result; +}; \ No newline at end of file diff --git a/Week_03/id_39/LeetCode_107_39.js b/Week_03/id_39/LeetCode_107_39.js new file mode 100644 index 00000000..3190adc1 --- /dev/null +++ b/Week_03/id_39/LeetCode_107_39.js @@ -0,0 +1,41 @@ +/** + * Definition for a binary tree node. + * function TreeNode(val) { + * this.val = val; + * this.left = this.right = null; + * } + */ +/** + * @param {TreeNode} root + * @return {number[][]} + * https://leetcode.com/problems/binary-tree-level-order-traversal-ii/ + */ +var levelOrderBottom = function(root) { + if (!root) { + return []; + } + let queue = [root]; + let levelNum = 1; + let result = []; + + while (queue.length) { + result.unshift([]); + let count = 0; + for (let i = 0; i < levelNum; i++) { + let node = queue.shift(); + if (node.val != null) { + result[0].push(node.val); + } + if (node.left) { + queue.push(node.left); + count++; + } + if (node.right) { + queue.push(node.right); + count++; + } + } + levelNum = count; + } + return result; +}; \ No newline at end of file diff --git a/Week_03/id_39/LeetCode_200_39.js b/Week_03/id_39/LeetCode_200_39.js new file mode 100644 index 00000000..0d3c8aef --- /dev/null +++ b/Week_03/id_39/LeetCode_200_39.js @@ -0,0 +1,101 @@ +/** + * @param {character[][]} grid + * @return {number} + * https://leetcode.com/problems/number-of-islands/ + */ + +/** + * 以下为 dfs递归染色解法 + */ +var dfs = function (grid, i, j) { + let direction = [[1, 0], [-1, 0], [0, 1], [0, -1]]; + grid[i][j] = '0'; + for (let h = 0; h < direction.length; h++) { + let x = direction[h][0]; + let y = direction[h][1]; + if (grid[i+x] && grid[i+x][j+y] == '1') { + grid[i+x][j+y] = '0'; + dfs(grid, i+x, j+y); + } + } +} + +var numIslands = function(grid) { + let count = 0; + for (let i = 0; i < grid.length; i++) { + for (let j = 0; j < grid[i].length; j++) { + if (grid[i][j] == '1') { + count++; + dfs(grid, i, j); + } + } + } + return count; +}; + + +/** + * 以下为用并查集的解法 + */ +class UnionFind{ + constructor(grid) { + let m = grid.length, n = grid[0].length; + this.count = 0; + this.parent = new Array(m*n).fill(-1); + this.rank = new Array(m*n).fill(0); + for (let i = 0; i < m; i++) { + for (let j = 0; j < n; j++) { + if (grid[i][j] == '1') { + this.parent[i * n + j] = i * n + j; + this.count++; + } + } + } + } + find(i) { + if (this.parent[i] != i) { + this.parent[i] = this.find(this.parent[i]); + } + return this.parent[i]; + } + union(x, y) { + let rootx = this.find(x); + let rooty = this.find(y); + if (rootx != rooty) { + if (this.rank[rootx] > this.rank[rooty]) { + this.parent[rooty] = rootx; + } else if (this.rank[rootx] < this.rank[rooty]) { + this.parent[rootx] = rooty; + } else { + this.parent[rooty] = rootx; + this.rank[rootx] += 1; + } + this.count--; + } + } +} + +var numIslands = function(grid) { + if (!grid || !grid[0]) { + return 0; + } + let uf = new UnionFind(grid); + let direction = [[1, 0], [-1, 0], [0, 1], [0, -1]]; + let m = grid.length, n = grid[0].length; + + for (let i = 0; i < m; i++) { + for (let j = 0; j < n; j++) { + if (grid[i][j] == '0') { + continue; + } + for (let d = 0; d < direction.length; d++) { + let nr = i + direction[d][0], nc = j + direction[d][1]; + if (nr >= 0 && nc >= 0 && nr < m && nc < n && grid[nr][nc] == '1') { + uf.union(i * n + j, nr * n + nc); + } + } + } + } + + return uf.count; +}; \ No newline at end of file diff --git a/Week_03/id_39/LeetCode_429_39.js b/Week_03/id_39/LeetCode_429_39.js new file mode 100644 index 00000000..aeeaa524 --- /dev/null +++ b/Week_03/id_39/LeetCode_429_39.js @@ -0,0 +1,43 @@ +/** + * // Definition for a Node. + * function Node(val,children) { + * this.val = val; + * this.children = children; + * }; + */ +/** + * @param {Node} root + * @return {number[][]} + * https://leetcode.com/problems/n-ary-tree-level-order-traversal/ + */ +var levelOrder = function(root) { + if (!root) { + return []; + } + let result = []; + + let queue = []; + let level = [root]; + let depth = -1; + + while (level.length) { + depth++; + result[depth] = []; + + while (level.length) { + let node = level.shift(); + result[depth].push(node.val); + + if (!node.children) { + continue; + } + for (let i = 0; i < node.children.length; i++) { + queue.push(node.children[i]); + } + } + + level = queue; + queue = []; + } + return result; +}; \ No newline at end of file diff --git a/Week_03/id_39/LeetCode_529_39.js b/Week_03/id_39/LeetCode_529_39.js new file mode 100644 index 00000000..dda59517 --- /dev/null +++ b/Week_03/id_39/LeetCode_529_39.js @@ -0,0 +1,37 @@ +/** + * @param {character[][]} board + * @param {number[]} click + * @return {character[][]} + * https://leetcode.com/problems/minesweeper/ + */ +var updateBoard = function(board, click) { + let m = board.length, n = board[0].length; + let direction = [[0, 1], [1, 0], [0, -1], [-1, 0], [1, 1], [-1, -1], [1, -1], [-1, 1]]; + + let cX = click[0]; + let cY = click[1]; + if (board[cX][cY] == 'M') { + board[cX][cY] = 'X'; + } + if (board[cX][cY] == 'E') { + let count = 0; + for (let i = 0; i < direction.length; i++) { + let x = cX + direction[i][0], y = cY + direction[i][1]; + if (x >= 0 && y >= 0 && x < m && y < n && board[x][y] == 'M') { + count++; + } + } + if (count == 0) { + board[cX][cY] = 'B'; + for (let i = 0; i < direction.length; i++) { + let x = cX + direction[i][0], y = cY + direction[i][1]; + if (x >= 0 && y >= 0 && x < m && y < n) { + updateBoard(board, [x, y]); + } + } + } else { + board[cX][cY] = count.toString(); + } + } + return board; +}; \ No newline at end of file diff --git a/Week_03/id_39/NOTE.md b/Week_03/id_39/NOTE.md index 107ea7d6..1dce625f 100644 --- a/Week_03/id_39/NOTE.md +++ b/Week_03/id_39/NOTE.md @@ -1 +1,14 @@ # 学习笔记 + +## 并查集 +- 并查集的逻辑理解起来不难 +- 但是写起来不是特别简单，虽然都是基础数据结构，但是还是不那么好写，尤其是带rank的，路径压缩还比较好理解，得多写几次 +- 岛屿的题目用dfs来做非常好理解，突然觉得递归这个之前觉得很难的东西，在算法题里反倒是最简单的了 +- 自己还是有很多成长的，加油~ + +## 树 +- 写了很多个按层遍历BFS的题，现在已经非常熟悉使用queue来做按层遍历的题 +- 之前觉得树对我是一个不小的难点，但是做的多了，都是套路化的应用dfs（stack）和bfs（queue） + +## 堆 +- 堆的应用其实不难，像java这种语言有直接提供优先队列使用倒是不复杂，但是像js这个，得自己实现一个大顶堆、小顶堆，是个不小的挑战。 \ No newline at end of file From 6f112224f8a8c2e3dbb0f6b33bbbc1c734781916 Mon Sep 17 00:00:00 2001 From: ziyun Date: Sun, 23 Jun 2019 23:01:03 +0800 Subject: [PATCH 2/2] add leetCode 329 --- Week_03/id_39/LeetCode_329_39.js | 41 ++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) create mode 100644 Week_03/id_39/LeetCode_329_39.js diff --git a/Week_03/id_39/LeetCode_329_39.js b/Week_03/id_39/LeetCode_329_39.js new file mode 100644 index 00000000..c87fd170 --- /dev/null +++ b/Week_03/id_39/LeetCode_329_39.js @@ -0,0 +1,41 @@ +/** + * @param {number[][]} matrix + * @return {number} + * https://leetcode.com/problems/longest-increasing-path-in-a-matrix/ + * dfs + 记忆化 + */ + +var direction = [[0, 1], [1, 0], [-1, 0], [0, -1]]; + +var dfs = function (matrix, i, j, memo) { + let m = matrix.length, n = matrix[0].length; + let index = i * n + j; + if (memo[index] != -1) { + return memo[index]; + } + let max = 1; + + for (let d = 0; d < direction.length; d++) { + let x = i + direction[d][0], y = j + direction[d][1]; + if (x >= 0 && y >= 0 && x < m && y < n && matrix[x][y] > matrix[i][j]) { + max = Math.max(max, dfs(matrix, x, y, memo) + 1); + } + } + memo[index] = max; + return max; +} + +var longestIncreasingPath = function(matrix) { + if (!matrix || !matrix.length) { + return 0; + } + let m = matrix.length, n = matrix[0].length; + let max = 1; + let memo = new Array(m*n).fill(-1); + for (let i = 0; i < m; i++) { + for (let j = 0; j < n; j++) { + max = Math.max(max, dfs(matrix, i, j, memo)); + } + } + return max; +}; \ No newline at end of file