From 29d2c6c7478b0d8593e9c172149736be03984dfc Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E5=B7=A6=E7=A8=8B=E4=BA=91?= Date: Thu, 17 Dec 2020 15:41:56 +0800 Subject: [PATCH] modify code --- src/class09_14/Code05_UnionFind.java | 69 +++++++ src/class09_14/Code06_IslandProblem.java | 238 +++++++++++++++++++++++ src/class10/Code01_UnionFind.java | 4 +- 3 files changed, 308 insertions(+), 3 deletions(-) create mode 100644 src/class09_14/Code05_UnionFind.java create mode 100644 src/class09_14/Code06_IslandProblem.java diff --git a/src/class09_14/Code05_UnionFind.java b/src/class09_14/Code05_UnionFind.java new file mode 100644 index 0000000..83d952a --- /dev/null +++ b/src/class09_14/Code05_UnionFind.java @@ -0,0 +1,69 @@ +package class09_14; + +import java.util.HashMap; +import java.util.List; +import java.util.Stack; + +public class Code05_UnionFind { + + public static class Node { + V value; + + public Node(V v) { + value = v; + } + } + + public static class UnionSet { + public HashMap> nodes; + public HashMap, Node> parents; + public HashMap, Integer> sizeMap; + + public UnionSet(List values) { + nodes = new HashMap<>(); + parents = new HashMap<>(); + sizeMap = new HashMap<>(); + for (V cur : values) { + Node node = new Node<>(cur); + nodes.put(cur, node); + parents.put(node, node); + sizeMap.put(node, 1); + } + } + + public Node findFather(Node cur) { + Stack> path = new Stack<>(); + while (cur != parents.get(cur)) { + path.push(cur); + cur = parents.get(cur); + } + while (!path.isEmpty()) { + parents.put(path.pop(), cur); + } + return cur; + } + + public boolean isSameSet(V a, V b) { + return findFather(nodes.get(a)) == findFather(nodes.get(b)); + } + + public void union(V a, V b) { + Node aHead = findFather(nodes.get(a)); + Node bHead = findFather(nodes.get(b)); + if (aHead != bHead) { + int aSetSize = sizeMap.get(aHead); + int bSetSize = sizeMap.get(bHead); + Node big = aSetSize >= bSetSize ? aHead : bHead; + Node small = big == aHead ? bHead : aHead; + parents.put(small, big); + sizeMap.put(big, aSetSize + bSetSize); + sizeMap.remove(small); + } + } + + public int sets() { + return sizeMap.size(); + } + + } +} diff --git a/src/class09_14/Code06_IslandProblem.java b/src/class09_14/Code06_IslandProblem.java new file mode 100644 index 0000000..757d36f --- /dev/null +++ b/src/class09_14/Code06_IslandProblem.java @@ -0,0 +1,238 @@ +package class09_14; + +import java.util.ArrayList; +import java.util.List; + +import class09_14.Code05_UnionFind.UnionSet; + +public class Code06_IslandProblem { + + public static int solve1(int[][] board) { + int islands = 0; + for (int i = 0; i < board.length; i++) { + for (int j = 0; j < board[0].length; j++) { + if (board[i][j] == 1) { + islands++; + infect(board, i, j); + } + } + } + return islands; + } + + public static void infect(int[][] board, int i, int j) { + if (i < 0 || i == board.length || j < 0 || j == board[0].length || board[i][j] != 1) { + return; + } + board[i][j] = 2; + infect(board, i - 1, j); + infect(board, i + 1, j); + infect(board, i, j - 1); + infect(board, i, j + 1); + } + + public static int solve2(int[][] board) { + int row = board.length; + int col = board[0].length; + Dot[][] dots = new Dot[row][col]; + List dotList = new ArrayList<>(); + for (int i = 0; i < row; i++) { + for (int j = 0; j < col; j++) { + dots[i][j] = new Dot(); + dotList.add(dots[i][j]); + } + } + UnionSet us = new UnionSet<>(dotList); + for (int j = 1; j < col; j++) { + if (board[0][j - 1] == 1 && board[0][j] == 1) { + us.union(dots[0][j - 1], dots[0][j]); + } + } + for (int i = 1; i < row; i++) { + if (board[i - 1][0] == 1 && board[i][0] == 1) { + us.union(dots[i - 1][0], dots[i][0]); + } + } + for (int i = 1; i < row; i++) { + for (int j = 1; j < col; j++) { + if (board[i][j] == 1) { + if (board[i][j - 1] == 1) { + us.union(dots[i][j - 1], dots[i][j]); + } + if (board[i - 1][j] == 1) { + us.union(dots[i - 1][j], dots[i][j]); + } + } + } + } + return us.sets(); + } + + public static class Dot { + + } + + public static int solve3(int[][] board) { + int row = board.length; + int col = board[0].length; + UnionFind uf = new UnionFind(board); + for (int j = 1; j < col; j++) { + if (board[0][j - 1] == 1 && board[0][j] == 1) { + uf.union(0, j - 1, 0, j); + } + } + for (int i = 1; i < row; i++) { + if (board[i - 1][0] == 1 && board[i][0] == 1) { + uf.union(i - 1, 0, i, 0); + } + } + for (int i = 1; i < row; i++) { + for (int j = 1; j < col; j++) { + if (board[i][j] == 1) { + if (board[i][j - 1] == 1) { + uf.union(i, j - 1, i, j); + } + if (board[i - 1][j] == 1) { + uf.union(i - 1, j, i, j); + } + } + } + } + return uf.sets(); + } + + public static class UnionFind { + private int[] parent; + private int[] size; + private int[] help; + private int col; + private int sets; + + public UnionFind(int[][] board) { + col = board[0].length; + sets = 0; + int row = board.length; + int len = row * col; + parent = new int[len]; + size = new int[len]; + help = new int[len]; + for (int r = 0; r < row; r++) { + for (int c = 0; c < col; c++) { + if (board[r][c] == 1) { + int i = index(r, c); + parent[i] = i; + size[i] = 1; + sets++; + } + } + } + } + + private int index(int r, int c) { + return r * col + c; + } + + private int find(int i) { + int hi = 0; + while (i != parent[i]) { + help[hi++] = i; + i = parent[i]; + } + for (hi--; hi >= 0; hi--) { + parent[help[hi]] = i; + } + return i; + } + + public void union(int r1, int c1, int r2, int c2) { + int i1 = index(r1, c1); + int i2 = index(r2, c2); + int f1 = find(i1); + int f2 = find(i2); + if (f1 != f2) { + if (size[f1] >= size[f2]) { + size[f1] += size[f2]; + parent[f2] = f1; + } else { + size[f2] += size[f1]; + parent[f1] = f2; + } + sets--; + } + } + + public int sets() { + return sets; + } + + } + + public static int[][] generateRandomMatrix(int row, int col) { + int[][] board = new int[row][col]; + for (int i = 0; i < row; i++) { + for (int j = 0; j < col; j++) { + board[i][j] = Math.random() < 0.5 ? 1 : 0; + } + } + return board; + } + + public static int[][] copy(int[][] board) { + int row = board.length; + int col = board[0].length; + int[][] ans = new int[row][col]; + for (int i = 0; i < row; i++) { + for (int j = 0; j < col; j++) { + ans[i][j] = board[i][j]; + } + } + return ans; + } + + public static void main(String[] args) { + int row = 1000; + int col = 1000; + int[][] board1 = generateRandomMatrix(row, col); + int[][] board2 = copy(board1); + int[][] board3 = copy(board1); + + long start = 0; + long end = 0; + start = System.currentTimeMillis(); + System.out.println(solve1(board1)); + end = System.currentTimeMillis(); + System.out.println((end - start) + " ms"); + System.out.println("==================="); + + start = System.currentTimeMillis(); + System.out.println(solve2(board2)); + end = System.currentTimeMillis(); + System.out.println((end - start) + " ms"); + System.out.println("==================="); + + start = System.currentTimeMillis(); + System.out.println(solve3(board3)); + end = System.currentTimeMillis(); + System.out.println((end - start) + " ms"); + System.out.println("==================="); + + row = 10000; + col = 10000; + board1 = generateRandomMatrix(row, col); + board3 = copy(board1); + + start = System.currentTimeMillis(); + System.out.println(solve1(board1)); + end = System.currentTimeMillis(); + System.out.println((end - start) + " ms"); + System.out.println("==================="); + + start = System.currentTimeMillis(); + System.out.println(solve3(board3)); + end = System.currentTimeMillis(); + System.out.println((end - start) + " ms"); + System.out.println("==================="); + + } + +} diff --git a/src/class10/Code01_UnionFind.java b/src/class10/Code01_UnionFind.java index 6e12590..937d185 100644 --- a/src/class10/Code01_UnionFind.java +++ b/src/class10/Code01_UnionFind.java @@ -30,15 +30,13 @@ public class Code01_UnionFind { sizeMap.put(node, 1); } } - - // 从点cur开始，一直往上找，找到不能再往上的代表点，返回 + public Node findFather(Node cur) { Stack> path = new Stack<>(); while (cur != parents.get(cur)) { path.push(cur); cur = parents.get(cur); } - // cur头节点 while (!path.isEmpty()) { parents.put(path.pop(), cur); }