递归到迭代帕斯卡三角形 [英] Recursive to iterative Pascal's triangle

问题描述

我想知道如何将递归函数/类转换为迭代函数/类.我已经制作了一个递归帕斯卡三角形，现在需要将其与迭代进行比较.

I wonder how to convert a recursive function/class to an iterative one. I have made a recursive Pascal's triangle, and now need to compare it to an iterative.

public class RecursivePascal extends ErrorPascal implements Pascal {
    private int n;
    RecursivePascal(int n) throws Exception {
        super(n);
        this.n = n;
    }
    public void printPascal() {
        printPascal(n, false);
    }
    public void printPascal(boolean upsideDown) {
        printPascal(n, upsideDown);
    }
    private void printPascal(int n, boolean upsideDown) {
        if (n == 0) {
            return;
        }
        if (!upsideDown) {
            printPascal(n - 1, upsideDown);
        }
        for (int i = 0; i < n; i++) {
            System.out.print(binom(n - 1, i) + (n == i + 1 ? "
" : " "));
        }
        if (upsideDown) {
            printPascal(n - 1, upsideDown);
        }
    }
    public int binom(int n, int k) {
        if (k == 0 || n == k) {
            return 1;
        }
        return binom(n - 1, k - 1) + binom(n - 1, k);
    }
}

我需要更改哪些内容才能使其迭代?我仍然有点不确定这是如何工作的.

What do I need to change in order to make it iterative? I'm still a little unsure of how this works.

推荐答案

将下面这两个函数插入到一个pascal类中.我测试了它并且它有效.Prateek Darmwal 发布的那个链接几乎是一回事.

Plug these two functions below into a pascal class. I tested it and it works. That link that Prateek Darmwal posted is pretty much the same thing.

public void nonRecursivePrint() {
    nonRecursivePrint(n, true);
}

public void nonRecursivePrint(int n, boolean upsideDown) {
    if (!upsideDown) {
        for (int j = 0; j < (n + 1); j++) {
            for (int i = 0; i < (j); i++) {
                System.out.print(binom(j - 1, i) + (j == i + 1 ? "
" : " "));
            }
        }
    } else {
        for (int j = n; j > 0; j--) {
            for (int i = 0; i < (j); i++) {
                System.out.print(binom(j - 1, i) + (j == i + 1 ? "
" : " "));
            }
        }
    }
}

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