最近打算换工作，还是需要补一下面试的基础知识，写了一些面试中可能会用到的常用算法、方法，以便复习
//99乘法表 /** * 1*1 * 1*1 1*2 * 1*1 1*2 1*3 * …… * */ private static void chengfabiao() { for(int i=1;i<=9;i++) { for(int j=1;j<=i;j++) { System.out.print(j+"*"+i+"="+i*j+";"); } System.out.println(); } } }
斐波那契数列：
//递归 private static int feibonaqie(int index) { // TODO Auto-generated method stub //0 1 1 2 3 5 8 13 21 int temp = 0; if(index == 0) { return 0; }else if(index == 1) { return 1; }else { temp = feibonaqie(index-2)+feibonaqie(index-1); //sum += temp; //count++; return temp; } } //循环 private static int feibonaqie2(int index) { // TODO Auto-generated method stub //0 1 1 2 3 5 8 13 21 int temp = 0; int a = 0,b = 1; if(index == 0) { return 0; }else if(index == 1) { return 1; }else { for(int i=2;i<=index;i++) { temp = a+b; a=b; b=temp; } //sum += temp; //count++; return temp; } }
/** * @author QiaoJiafei * @version 创建时间：2016年3月9日 下午12:02:09 * 类说明 获取数组平衡点 */ public class TestArrayBlance { public static void main(String[] args) { int arr[] = {10,5,4,1,3,7}; getBlance(arr); } private static void getBlance(int arry[]) { // TODO Auto-generated method stub int sum = 0; int subsum = 0; List<Integer> list = new ArrayList<Integer>(); for(int i=0;i<arry.length;i++) { sum += arry[i]; } for(int i=0;i<arry.length;i++) { subsum += arry[i]; if(subsum == sum-subsum){ list.add(i); } for(int j=i+1;j<arry.length;j++) { if(subsum == sum-subsum-arry[j]) { list.add(j); } } } System.out.println(list.size()+";"+list.get(0)); } }
/* * 4，模拟一个trim功能一致的方法。去除字符串两端的空白 * 思路： * 1，定义两个变量。 * 一个变量作为从头开始判断字符串空格的角标。不断++。 * 一个变量作为从尾开始判断字符串空格的角标。不断--。 * 2,判断到不是空格为止，取头尾之间的字符串即可。 */ public class StringTest_4 { /** * @param args */ public static void main(String[] args) { String s = " ab c "; s = myTrim(s); System.out.println("-" + s + "-"); } public static String myTrim(String s) { int start = 0, end = s.length() - 1; while (start <= end && s.charAt(start) == ' ') { start++; } while (start <= end && s.charAt(end) == ' ') { end--; } return s.substring(start, end + 1); } }
/** * @author QiaoJiafei * @version 创建时间：2016年1月25日 上午11:52:50 * 类说明 获取最大子串。思路每次循环从子串的第一个位置开始start，以子串总长度-i结束end。整体依次往右移，这样循环。i代表循环次数，从0开始 */ public class StringContents { public static void main(String[] args) { // TODO Auto-generated method stub String s1 = "asdflkjljsodfjiosdjf"; String s2 = "jsodfjia"; fff(s1, s2); } public static void fff(String s1, String s2) { boolean flag = false; int len = s2.length(); for (int i= 0; i< len; i++) { for (int a = 0,b=len-i; b<=len; a++,b++) { String s = s2.substring(a, b); //System.out.println(s); if(s1.contains(s)) { System.out.println("index:"+s1.indexOf(s)); System.out.println(s); flag = true; return; } } if(flag) { break; } } } }
public class Test {
public static void main(String args[]) { int [] arry = {5,45,2,1,8,6,12}; Test t = new Test(); } //冒泡排序 void maoP(int a[]) { int temp = 0; for (int i=0;i<a.length-1;i++) { for(int j=0; j<a.length-1-i; j++) { if (a[j] > a[j+1]) { temp = a[j]; a[j] = a[j+1]; a[j+1] = temp; } } } } void prin(int a[]) { for (int i=0; i<a.length; i++) { System.out.print(a[i] + " "); } } //选择排序 void xuanZ(int a[]) { for(int i=0; i<a.length; i++) { //int p = a[i]; int temp = 0; for (int j=i+1; j< a.length; j++) { if (a[j] < a[i]) { temp = a[i]; a[i] = a[j]; a[j] =temp; //a[j] = temp; } } } } //快速排序 void kuaiS(int []a, int low, int high) { if (low < high) { int mid = kP(a, low, high); kuaiS(a, low, mid-1); kuaiS(a, mid+1, high); } } int kP(int []a, int low, int high) { int temp = a[low]; while (low < high) { while (low < high && temp <= a[high]) { high--; } a[low] = a[high]; while (low < high && temp >= a[low]) { low++; } a[high] = a[low]; } a[low] = temp; return low; } //二分查找-普通循环 int erF(int a[], int tp) { int mid = a.length/2; int start = 0; int end = a.length-1; while (start <= end) { mid = (end - start)/2 + start; if (tp == a[mid]) { return mid; } else if (tp < a[mid]) { end = mid -1; } else if (tp > a[mid]) { start = mid + 1; } else { return mid; } } return -1; } //二分查找-递归 int erFeD(int a[],int dex, int start, int end) { int mid = (end - start)/2 + start; if (a[mid] == dex) { return mid; } if (end <= start) { return -1; } else if (a[mid] > dex) { return erFeD(a, dex, start, mid-1); } else if (a[mid] < dex) { return erFeD(a, dex, mid+1, end); } return -1; } //顺序查找 int shunX(int a[], int dex) { for (int i=0; i< a.length-1; i++) { if(a[i] == dex) { return i; } } return -1; } //阶乘 void jieC(int temp) { int f = 1; for (int i=1; i<=temp; i++) { f = f*i; } System.out.println(f); } //阶乘相加 void JieChJ(int temp) { int sum = 0; int f = 1; for (int i=1; i<=temp; i++) { f *= i; sum += f; } System.out.println(sum); } //阶乘相加2 int jieC1(int temp) { int f = 1; for (int i=1; i<=temp; i++) { f = f*i; } return f; } void jieC2(int temp) { int sum = 0; for (int i=1; i<=temp; i++) { sum += jieC1(i); } System.out.println(sum); } //1~100的质数 void zhiS() { for (int i=1; i<100; i+=2) { boolean flag = true; for (int j=2; j<i; j++) { if (i%j == 0) { flag = false; break; } } if (!flag) { continue; } System.out.print(i + " "); } } //1~100前5个被3整除的数 void zhengC() { int temp = 0; for (int i=1; i<=100; i++) { if (i%3 == 0) { temp++; System.out.print(i + " "); } if (temp == 5) { break; } } } }
输出：
0
12
345
6789
static void fString() { String s = "0123456789"; int sum = 0; for(int i=0;i<4;i++) { sum +=i; System.out.println(s.substring(sum, sum+i+1)); } }
一个数组中的元素出现了3次的值
private static int getArrayValue(int array[]) { // TODO Auto-generated method stub int value = 0; for(int i=0;i<array.length;i++) { int count = 0; for(int j=0;j<array.length;j++) { if (array[i] == array[j]) { count ++; } } if(count == 3) { value = array[i]; } } return value; }
大小写转换
public static void main(String[] args) { String u[] = {"零","壹","贰","叁","肆","伍","陆","柒","捌","玖"}; int num = 123433568; String s = String.valueOf(num); char c[] =s.toCharArray(); for(int i=0;i<c.length;i++) { int j = Integer.parseInt(String.valueOf(c[i])); System.out.print(u[j]); } }