Question

我正在尝试创建Pascal的Triangle，并创建“ return pascalTriangle（row-1，col-1）+ pascalTriangle（row-1，col）;”行。在返回帕斯卡三角形中的int值的递归方法中，导致线程“ main” java.lang.StackOverflowError中的异常。它只打印一行“ 1”，然后对其他行抛出异常。我需要修复什么，使其不会引发任何异常并形成帕斯卡的三角形？这是我的代码：

import java.util.Scanner;

/**
 * This program takes n input from the user, and forms Pascal's Triangle in n number of rows that the user entered.
 */
public class DD_PascalsTriangle {

    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);
        System.out.println("Enter an integer: ");
        int n = scanner.nextInt(); //the number of rows created in the Pascal's Triangle
        printTriangle(n); //print Pascal's Triangle
    }

    /**
     *
     * @param row rows in Pascal's Triangle
     * @param col columns in Pascal's Triangle
     * @return values in the Pascal's Triangle
     */
    private static int pascalTriangle(int row, int col) {
        if (col==0 || col==row) return 1; //base case
        else return pascalTriangle(row - 1, col - 1) + pascalTriangle(row - 1, col); //create the values in Pascal's Triangle
    }

    /**
     *
     * @param n the input from the user (aka the n number of rows in Pascal's Triangle)
     */
    private static void printTriangle(int n){
        for (int row=0; row<n; row++){
            for (int col=0; col<n;col++){
                System.out.println(pascalTriangle(row,col) + " ");
            }
            System.out.println();
        }
    }
}

Answer 1

似乎您的代码将进入无限循环，因为您为内部循环保留了错误的条件哪个调用和调用......填充堆栈内存比JVM分配的更多

为避免帕斯卡三角形的堆积溢出错误和完美形状，您只需添加一个额外的循环并更改内部循环的条件即可。

public static void printTriangle（int n）{ for（int row = 0; row

        //Added Spacer loop for getting perfect shape for  pascal triangle
        for(int spacer =n ; spacer > row ; spacer--){
            System.out.print(" ");
        }



       for (int col=0; col <= row; col++){
           System.out.print(pascalTriangle(row,col) + " ");
       }
       System.out.println();
   }

Answer 2

更改第二个循环以迭代到上一行而不是n。

   public static void printTriangle(int n){
       for (int row = 0; row < n; row++) {
           for (int col=0; col <= row; col++){
               System.out.print(pascalTriangle(row,col) + " ");
           }
           System.out.println();
       }

递归方法导致java.lang.StackOverflowError

2 个答案: