1.汉诺塔问题：

import java.util.Scanner;public class Hanoi {        public static void main(String[] args) {        int n;        Scanner cin = new Scanner(System.in);        while(cin.hasNext()){            n = cin.nextInt();            hanoi(n, 'A', 'C', 'B');        }    }        public static void hanoi(int n, char a, char b, char c){        if(n == 1){            move(a, b);            return;        }        hanoi(n-1, a, c, b);        move(a, b);        hanoi(n-1, c, b, a);    }        public static void move(char a, char b){        System.out.println("move " + a + " to " + b);    }}

 2.归并排序：

import java.util.Scanner;public class MergeSort {    public static int[] a, b;    public static void main(String[] args) {        int l;        Scanner cin = new Scanner(System.in);        while(cin.hasNext()){            l = cin.nextInt();            a = new int[l + 1];            b = new int[l + 1];                        for(int i = 1; i <= l; i++){                a[i] = cin.nextInt();            }            ms(1, l);            for(int i = 1; i <= l; i++){                System.out.printf("%d ", a[i]);            }            System.out.println();        }    }    public static void mergeSort(int l, int m, int r){        int i = l, j = m + 1, k;        k = l;        while(i <= m && j <= r){            if(a[i] <= a[j])                b[k++] = a[i++];            else                b[k++] = a[j++];        }        while(i <= m){            b[k] = a[i];            k++; i++;        }        while(j <= r){            b[k] = a[j];            k++; j++;        }        for(k = l; k <= r; k++){            a[k] = b[k];        }    }    public static void ms(int l, int r){        if(l < r){            int m = (l + r) / 2;            ms(l, m);            ms(m+1, r);            mergeSort(l, m, r);        }    }}

 3.求众数：

import java.util.Arrays;import java.util.Comparator;import java.util.Scanner;import sun.misc.Compare;import sun.misc.Sort;/** * @author Administrator * */class Num{        public int value;    public int count;        public Num() {        value = 0;        count = 0;    }    public Num(int value, int count) {        super();        this.value = value;        this.count = count;    }            public int getValue() {        return value;    }    public void setValue(int value) {        this.value = value;    }    public int getCount() {        return count;    }    public void setCount(int count) {        this.count = count;    }    public String toString() {        return "value = " + value + "\tcount = " + count;    }}public class Zhongshu {    static int[] num;    static Num[] ans;    static{        ans = new Num[10010];        for(int i = 0; i < 10010; i++){            ans[i] = new Num();        }    }    public static void main(String[] args) {        int N;        Scanner cin = new Scanner(System.in);        while(cin.hasNext()){            N = cin.nextInt();            num = new int[N];            for(int i = 0; i < N; i++){                num[i] = cin.nextInt();            }            Arrays.sort(num);            int value = num[0], last = 0, count, k = 0;            for(int i = 1; i < N; i++){                if(value != num[i]){                    count = i - last;                    ans[k].setCount(count);                    ans[k].setValue(value);                    k++;                    last = i;                    value = num[i];                }            }            count = N - last;            ans[k].setCount(count);            ans[k].setValue(value);            k++;//            for(int i = 0; i < k; i++){//                System.out.println(ans[i]);//            }            Arrays.sort(ans, 0, k, new MyComparator());            for(int i = 0; i < k; i++){                System.out.println(ans[i]);            }        }            }}class MyComparator implements Comparator{    public int compare(Object a, Object b) {        if(a == null || b == null){            System.out.println("无奈啊！！！");        }        Num o1 = (Num)a;        Num o2 = (Num)b;        if(o1.getCount() != o2.getCount())            return o1.getCount() - o2.getCount();        else            return o1.getValue() - o2.getValue();    }    }

 4.约瑟夫环：

import java.util.ArrayList;import java.util.Scanner;public class 约瑟夫环 {    public static ArrayList
     
      arrayList;    static{        arrayList = new ArrayList
      
       ();    }    static void init(int n){        arrayList.clear();        for(int i = 1; i <= n; i++){            arrayList.add(i);        }    }    static int work(int ele, int pos){        if(arrayList.size() == 1)            return arrayList.get(0);        else{            int cur = (pos + ele - 1)%arrayList.size();            if(cur == 0)                cur = arrayList.size();                        System.out.printf("%d死了\n", arrayList.get(cur - 1));            arrayList.remove(cur - 1);            //System.out.println(arrayList.size());            return work(ele, cur%arrayList.size() == 0?                            arrayList.size() : cur%arrayList.size());        }    }        public static void main(String[] args) {        Scanner cin = new Scanner(System.in);        int m, n;        while(cin.hasNext()){            n = cin.nextInt();            m = cin.nextInt();            init(n);            System.out.printf("最后%d活着\n", work(m, 1));        }    }}