手写杨辉三角

今天回答某位博主悬赏的题目, 我觉得我代码写的挺好的,很有价值, 脑力劳动嘛, 发个博客保存一下

收获

提示：递归还真不适应人脑,想半天

1. 代码谁都能写出来,但是自己写的就感觉很有成就感
2. 大概花了快一个小时了,保存一下
3. 话说悬赏的问题, 解题的时候也没采纳任何答案, 那你悬赏给啥, 抠门

package com.ajieyao.modules;

import java.util.Arrays;

public class Demo {

    public static void main(String[] args) {
        Yang yang = new Yang(3,4,5);
        yang.printTriangle();
        System.out.println(yang.caculat());
        yang.expandString();
        int i = yang.expandCaculate();
        System.out.println(i);
    }
    static class Yang{
        private int a,b,n;
        private int[][] arr;
        public Yang() {
        }
        public Yang(int a, int b, int n) {
            this.a = a;
            this.b = b;
            this.n = n;
            this.arr = getTriangle(n);
        }
        private double caculat(){
            return Math.pow(a+b, n);
        }
        private void printTriangle(){
            for (int i = 0; i < this.arr.length; i++) {
                System.out.println(Arrays.toString(this.arr[i]));
            }
        }
        private int[][] getTriangle(int n)  {
            int[][] array = new int[n+1][];
            for (int i = 0; i < array.length; i++) {
                array[i] = getNextRow(i);
            }
            return array;
        }
        private int[] getNextRow(int n)  {
            if(n == 0){
                int[] a = {1};
                return a;
            }
            if(n == 1){
                int[] a = {1,1};
                return a;
            }
            if(n == 2){
                int[] a = {1,2,1};
                return a;
            }
            int[] row = getNextRow(n-1);
            int[] ints = new int[row.length + 1];
            //第一个数字不需要计算 就取1
            ints[0] = 1;
            //sum存储的是上一个数组的计算结果，从一个开始，每次计算当前元素与后一个元素的和
            int[] sum = new int[row.length];
            for (int i = 0; i < row.length; i++) {
                int s = 1;
                //最后一个数字不需要计算 就取本身
                if(i == row.length-1){
                    s = row[i];
                }else{
                    s = row[i]+row[i+1];
                }
                sum[i] = s;
            }
            for (int i = 0; i < sum.length; i++) {
                ints[i+1] = sum[i];
            }
            return ints;
        }
        private String expandString(){
            StringBuffer sb = new StringBuffer("");
            int[] row = this.arr[this.arr.length-1];
            int c = this.n;
            for (int i = 0; i < row.length; i++) {
                int n = row[i];
                sb.append(n);
                if(c != 0){
                    sb.append("*");
                    sb.append(a);
                    sb.append("^");
                    sb.append(c);
                }
                if(i != 0){
                    sb.append("*");
                    sb.append(b);
                    sb.append("^");
                    sb.append(i);
                }
                if(i != row.length - 1){
                    sb.append("  +  ");
                }
                c--;
            }
            System.out.println(sb);
            return sb.toString();
        }
        private int expandCaculate(){
            int[] row = this.arr[this.arr.length-1];
            int c = this.n;
            int count = 0;
            for (int i = 0; i < row.length; i++) {
                int n = row[i];
                count += n*Math.pow(a, c)*Math.pow(b, i);
                c--;
            }
            return count;
        }
    }

}