Google-APAC2015-"super 2048"

今天得知Sitong拿到了FB和Google的offer，觉得很强，恭喜恭喜。自己还得加把劲啊！

宇妹（这里宇妹和托雷斯“托妞”是一种概念 =W=）说春季想跳槽到LinkedIn，于是呼唤我和他一起刷Leetcode。我愉快地答应了。熟能生巧嘛。

早上和Parker聊了一下，他说他prefer中型公司，比如dropbox, LinkedIn，因为小公司的package好、可以学到更多东西而且可能IPO。大神果然是比我们高到不知道哪里去了。

下午在Silo写代码，很快就把2048这道题目写好了，没什么难度，上题：

原题：super 2048

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#1 题目理解：

N * N的2048游戏，然后给定移动方向，输出移动结果。（= 。=，如果没有玩过这个游戏赶紧去google一下2048）

一看题目的描述就知道是中国人写的，因为里面用了(no zuo no die)，哈哈哈。果然是google在中国区的招聘题目，这么接地气。

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#2 算法：

这道题目还是挺简单明了的：

假设DIR == RIGHT，设定行指针是i，非空列指针是j，元素指针是p1, p2。

从右到左开始搜索，遇到非零元素，赋值p1；再次遇到，赋值p2。

只有p1 != null && p2 != null才继续操作。

如果&p1 == &p2，那么加起来，&j = &p1 + &p2，j--，把p1设为p2前一个。

如果&p1 != &p2，&j = &p1, j--，把p1设为p2。

记得把剩下的那个p1放到对应的 “ j ” 处。

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#3 数据结构：

int[][] board

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#4 代码：

import java.util.*;
import java.io.*;

public class Solution {
public static void main(String[] args) {
File inFile = new File("B-large-practice.in");
File outFile = new File("B-large-practice.out");
try {
BufferedReader br = new BufferedReader(new FileReader(inFile));
BufferedWriter bw = new BufferedWriter(new FileWriter(outFile));
int T = Integer.parseInt(br.readLine());
for (int i = 1; i <= T; i++) {
String line = br.readLine();
String[] parts = line.split("\\s");
int N = Integer.parseInt(parts[0]);
String DIR = parts[1];
String[] lines = new String
;
for (int j = 0; j < N; j++) {
lines[j] = br.readLine();
}
int[][] board = getBoard(lines);
bw.write("Case #" + i + ":\n" + solve(N, DIR, board));
}
bw.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}

// solve the super-2048
public static String solve(int N, String DIR, int[][] board) {
String s = "";
switch(DIR) {
case "up":
s = up(N, board);
break;
case "down":
s = down(N, board);
break;
case "left":
s = left(N, board);
break;
case "right":
s = right(N, board);
break;
default:
break;
}
return s;
}

// move right
public static String right(int N, int[][] board) {
for (int i = 0; i < N; i++) {
int j = N-1;
int p1 = N-1;
int p2;
while (true) {
while (p1 >= 0 && board[i][p1] == 0) p1--;
if (p1 < 0) break;
p2 = p1 - 1;
while (p2 >= 0 && board[i][p2] == 0) p2--;
if (p2 < 0) break;
if (board[i][p1] == board[i][p2]) {
board[i][j] = 2 * board[i][p1];
p1 = p2 - 1;
}
else {
board[i][j] = board[i][p1];
p1 = p2;
}
j--;
}
if (p1 >= 0) {
board[i][j] = board[i][p1];
j--;
}
while (j >= 0 && j < N) {
board[i][j] = 0;
j--;
}
}
return boardToStr(board);
}

// move left
public static String left(int N, int[][] board) {
for (int i = 0; i < N; i++) {
int j = 0;
int p1 = 0;
int p2;
while (true) {
while (p1 < N && board[i][p1] == 0) p1++;
if (p1 >= N) break;
p2 = p1 + 1;
while (p2 < N && board[i][p2] == 0) p2++;
if (p2 >= N) break;
if (board[i][p1] == board[i][p2]) {
board[i][j] = 2 * board[i][p1];
p1 = p2 + 1;
}
else {
board[i][j] = board[i][p1];
p1 = p2;
}
j++;
}
if (p1 < N) {
board[i][j] = board[i][p1];
j++;
}
while (j >= 0 && j < N) {
board[i][j] = 0;
j++;
}
}
return boardToStr(board);
}

// move down
public static String down(int N, int[][] board) {
for (int j = 0; j < N; j++) {
int i = N-1;
int p1 = N-1;
int p2;
while (true) {
while (p1 >= 0 && board[p1][j] == 0) p1--;
if (p1 < 0) break;
p2 = p1 - 1;
while (p2 >= 0 && board[p2][j] == 0) p2--;
if (p2 < 0) break;
if (board[p1][j] == board[p2][j]) {
board[i][j] = 2 * board[p1][j];
p1 = p2 - 1;
}
else {
board[i][j] = board[p1][j];
p1 = p2;
}
i--;
}
if (p1 >= 0) {
board[i][j] = board[p1][j];
i--;
}
while (i >= 0 && i < N) {
board[i][j] = 0;
i--;
}
}
return boardToStr(board);
}

// move up
public static String up(int N, int[][] board) {
for (int j = 0; j < N; j++) {
int i = 0;
int p1 = 0;
int p2;
while (true) {
while (p1 < N && board[p1][j] == 0) p1++;
if (p1 >= N) break;
p2 = p1 + 1;
while (p2 < N && board[p2][j] == 0) p2++;
if (p2 >= N) break;
if (board[p1][j] == board[p2][j]) {
board[i][j] = 2 * board[p1][j];
p1 = p2 + 1;
}
else {
board[i][j] = board[p1][j];
p1 = p2;
}
i++;
}
if (p1 < N) {
board[i][j] = board[p1][j];
i++;
}
while (i >= 0 && i < N) {
board[i][j] = 0;
i++;
}
}
return boardToStr(board);
}

// convert board into string
public static String boardToStr(int[][] board) {
int N = board.length;
StringBuilder sb = new StringBuilder();
for (int i = 0; i < N; i++) {
for (int j = 0; j < N; j++) {
sb.append(board[i][j] + " ");
}
sb.append("\n");
}
return sb.toString();
}

// convert the string into board
public static int[][] getBoard(String[] lines) {
int N = lines.length;
int[][] board = new int

;
for (int i = 0; i < N; i++) {
String[] parts = lines[i].split("\\s");
for (int j = 0; j < N; j++) {
board[i][j] = Integer.parseInt(parts[j]);
}
}
return board;
}
}