剑指offer笔记

Posted 2022-11-27 answerhfh

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面试题1：实现singleton模式

代码实现：
public class Singleton
private static Singleton instance = null;
private static Object syncObj = new Object();
private Singleton()

public static Singleton getInstance()
if (instance == null)
synchronized (syncObj)
if (instance == null)
instance = new Singleton();

return instance;

强烈推荐：静态构造方法

public class Singleton1
private static Singleton1 instance = new Singleton1();
private Singleton1()

public static Singleton1 getInstance()
return instance;

面试题3：二维数组中查找

代码：

public static boolean find(int[][] arr, int rows, int columns, int number)
boolean found = false;
if (arr == null || rows == 0 || columns == 0)
return found;

int row = 0;
int column = columns - 1;
while (row < rows && column >= 0)
if (arr[row][column] == number)
found = true;
return found;
else if (arr[row][column] > number)
--column;
else
++row;

return found;

面试题4：替换空格

代码：

public static char[] replaceBlank(char[] ch)
int originLength = 0;
int i = 0;
int numberOfBlank = 0;
while (ch[i] != '\\0')
originLength++;
if (ch[i] == ' ')
numberOfBlank++;

i++;

int newLength = originLength + 2 * numberOfBlank;
if (ch.length < newLength)
return null;

int indexOfOrigin = originLength - 1;
int indexOfNew = newLength - 1;
while (indexOfOrigin >= 0 && indexOfNew > indexOfOrigin)
if (ch[indexOfOrigin] == ' ')
ch[indexOfNew--] = '0';
ch[indexOfNew--] = '2';
ch[indexOfNew--] = '%';
else
ch[indexOfNew--] = ch[indexOfOrigin];

indexOfOrigin--;

return ch;

/**
* 合并两个有序数组A1、A2, A1有足够多的空余空间 O(n)
*/
public static int[] mergeArray(int[] a1,int a2)
int i = 0;
int a1Length = 0;
while (a1[i++] != '\\0')
a1Length++;

a1Length--;
int a2Length = a2.length - 1;
int newLength = a1Length + a2Length + 1;

while (newLength >= 0)
if (a1Length < 0 && a2Length >= 0)
a1[newLength--] = a2[a2Length--];
continue;

if (a2[a2Length] >= a1[a1Length])
a1[newLength--] = a2[a2Length--];
else
a1[newLength--] = a1[a1Length--];

return a1;