这几天笔试常考算法

来源：互联网发布：蜗居海藻知乎编辑：程序博客网时间：2024/04/29 19:23

1.求两个数公约数

public class Gongyue {    public static void main(String args[]){        int max = getMaxGongyue(11,12);        System.out.println(max);    }    public static int getMaxGongyue(int a, int n) {        if (a < n) {            int temp = a;            a = n;            n = temp;        }        while(a%n!=0){            int temp = a%n;            a = n;            n = temp;        }        return n;    }}

2.快速排序

public class Kuaipai {    public int[] sortQ(int[] temp, int low, int high) {        int pos;        if (low < high) {            pos = trans(temp, low, high);            sortQ(temp, low, pos - 1);            sortQ(temp, pos + 1, high);        }        return temp;    }    public int trans(int[] temp, int left, int right) {        int prvotkey = temp[left];        while (left < right) {            while (temp[right] >= prvotkey && left < right) {                right--;            }            temp[left] = temp[right];            while (temp[left] <= prvotkey && left < right) {                left++;            }            temp[right] = temp[left];        }        temp[left] = prvotkey;        return left;    }    public static void main(String args[]) {        int[] temp = { 6, 1, 9, 4, 10, 13 };        int[] sorts = new Kuaipai().sortQ(temp, 0, 5);        for (int i = 0; i < sorts.length; i++) {            System.out.println(sorts[i]);        }    }}

3.字母全排列，例如abc这3字母，可以排列成：abc，bac，cba等

public class QuanPai {    public static void permutation(char[] buf, int start, int end) {        if (start == end) {// 当只要求对数组中一个字母进行全排列时，只要就按该数组输出即可            for (int i = 0; i <= end; i++) {                System.out.print(buf[i]);            }            System.out.println();        } else {// 多个字母全排列            for (int i = start; i <= end; i++) {                char temp = buf[start];// 交换数组第一个元素与后续的元素                buf[start] = buf[i];                buf[i] = temp;                permutation(buf, start + 1, end);// 后续元素递归全排列                temp = buf[start];// 将交换后的数组还原                buf[start] = buf[i];                buf[i] = temp;            }        }    }    public static void main(String args[]){        char[] buf = {'a','b','c','d'};        permutation(buf,0,3);    }}

4.十进制转2进制，倒序2进制数，再输出对应的10进制

public class Ten2Two {    public static void main(String args[]){        String s = getTwo(23);        char[] cs = s.toCharArray();        System.out.println(cs);        for(int i=0;i<cs.length/2;i++){            char temp = cs[i];            cs[i] = cs[cs.length-1-i];            cs[cs.length-1-i] = temp;        }        System.out.println(cs);        int sum = 0;        for(int i=0;i<cs.length;i++){            sum = 2*sum+Integer.parseInt(cs[i]+"");        }        System.out.println(sum);    }    public static String getTwo(int t){        StringBuffer sb = new StringBuffer();        while(t!=0){            sb.insert(0, t % 2);            t = t/2;        }        return sb.toString();    }}

5.给你一个数字序列，要求找到最大的数放中间，其余数按大小顺序依次放该数的左边和右边

public class SpaTestOne {    public static void main(String args[]) {        int[] a = { 1, 45, 23, 74, 4, 32, 55,66 };        maoPao(a);        printAll(a);    }    /**     * 输出所有数组元素     * @param array     */    public static void printArray(int[] array) {        for (int i = 0; i < array.length; i++) {            System.out.print(array[i] + " ");        }    }    /**     * 按题目条件输出数据     * @param array  已从小到大排好序数组     */    public static void printAll(int[] array) {        int[] temp = new int[array.length];        int tempindex = 0;        for (int i = 0; i < array.length / 2;i++) {            temp[i] = array[tempindex];            temp[array.length - i-1] = array[tempindex + 1];            tempindex=tempindex+2;        }        temp[array.length / 2] = array[array.length - 1];        printArray(temp);    }    //冒泡进行排序    public static void maoPao(int[] array) {        for (int i = 0; i < array.length; i++) {            for (int j = 1; j < array.length - i; j++) {                //比较相邻数大小                if (array[j - 1] > array[j]) {                    //交换                    int temp = array[j - 1];                    array[j - 1] = array[j];                    array[j] = temp;                }            }        }    }}

0 0