1.斐波那契数列
package com.luna.base; public class BirthRabbit { public static void main(String[] args) { int i = 1; for (i = 1; i <= 20; i++) { System.out.println("兔子第" + i + "个月的总数为:" + f(i)); } } public static int f(int x) { if (x == 1 || x == 2) { return 1; } else { return f(x - 1) + f(x - 2); } } }2.从1到100相加
package com.luna.base; public class Plus { public int sum(int i) { if (i == 1) { return 1; } return i + sum(i - 1); } public static void main(String[] args) { Plus plus = new Plus(); System.out.println("计算结果：" + plus.sum(100) + "!"); } }3.100的阶乘
package com.luna.base; import java.math.BigInteger; public class LoopMutiply { public BigInteger sum(int i) { if (i == 1) { return BigInteger.ONE; } return BigInteger.valueOf(i).multiply(sum(i - 1)); } public static void main(String[] args) { LoopMutiply test = new LoopMutiply(); try { System.out.println("计算结果：" + test.sum(50) + "!"); } catch (Exception e) { e.printStackTrace(); } } }4.有序数组a、b合并成一个新的有序数组
package com.luna.base; public class ArraySort { public static void main(String[] args) { int[] a = { 1, 3, 4 }; int[] b = { 2, 3, 5, 6 }; int[] c = mergeArray(a, b); for (int n : c) { System.out.print(n + " "); } } // 合并数组 public static int[] mergeArray(int[] a, int[] b) { int result[] = new int[a.length + b.length]; if (checkSort(a) && checkSort(b)) { // 说明ab数组都是有序的数组 // 定义两个游标 int i = 0, j = 0, k = 0; while (i < a.length && j < b.length) { if (a[i] <= b[j]) { result[k++] = a[i++]; } else { result[k++] = b[j++]; } } while (i < a.length) { // 说明a数组还有剩余 result[k++] = a[i++]; } while (j < b.length) { result[k++] = b[j++]; } } return result; } // 检查一个数组是否是有序1 2 3 public static boolean checkSort(int[] a) { boolean flag = false;// 默认不是有序的 for (int i = 0; i < a.length - 1; i++) { if (a[i] > a[i + 1]) { // 说明不是有序的 flag = false; break; } else { flag = true; } } return flag; } }5.归并排序算法实现
package com.luna.base; public class MergingSort { public static void sort(int[] data, int left, int right) { if (left < right) { // 首先找出中间的索引 int center = (left + right) / 2; // 对中间索引左边的数组进行递归 sort(data, left, center); // 对中间索引右边的数组进行递归 sort(data, center + 1, right); // 合并 merge(data, left, center, right); } } public static void merge(int[] data, int left, int center, int right) { int[] tmpArr = new int[data.length]; int mid = center + 1; // third记录中间数组的索引 int third = left; int tmp = left; while (left <= center && mid <= right) { // 将两个数组中取出最小的数放入中间数组 if (data[left] <= data[mid]) { tmpArr[third++] = data[left++]; } else { tmpArr[third++] = data[mid++]; } } // 剩余部分依次放入中间数组 while (mid <= right) { tmpArr[third++] = data[mid++]; } while (left <= center) { tmpArr[third++] = data[left++]; } while(tmp <= right){ data[tmp] = tmpArr[tmp++]; } } public static void main(String[] args) { int[] a = { 3, 2, 5, 4 }; sort(a, 0, a.length - 1); for (int i = 0; i < a.length; i++) { System.out.print(a[i] + " "); } } } 更多排序算法的实现，请进传送门→
原文地址： https://blog.csdn.net/u0/article/details/
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