用二维数组打印出杨辉三角

 1 let readline = require("readline-sync");
 2 console.log("请输入杨辉三角的行数：");
 3 let line = parseInt(readline.question(""));
 4 console.log("杨辉三角如下：***************************************************");
 5 let strSpace = "";//用于存储空格的字符串
 6 let strNum = "";//用于存储杨辉三角的字符串
 7 
 8 let arr = new Array(line);//创建一维数组 
 9 
10 //创建二维数组  
11 for (let i = 0; i < arr.length; i++)
12 {
13     arr[i] = new Array(i + 1);
14 }
15 //控制二维数组的行数
16 for (let i = 0; i < arr.length; i++)
17 {
18     for (let k = 1; k < line - i; k++) //控制前面空格数量
19     {
20         strSpace = strSpace + "  ";
21     }
22     for (let j = 0; j < arr[i].length; j++)
23     {
24         //判断每行的数组的第一个和最后一个都为1  
25         if (j == 0 || i == j)
26         {
27             arr[i][j] = 1;
28         }
29         else    //规律,里面数字的规律
30         {
31             arr[i][j] = arr[i - 1][j - 1] + arr[i - 1][j];
32             
33         }
34         strNum += arr[i][j] + " ";//把数组放在字符串
35         strNum += " " + " ";  //在累加空格
36     }
37     console.log(strSpace + strNum);
38     //下面是每次循环清空
39     strNum = "";
40     strSpace = "";
41 }