Question

我正在尝试在Java中实现this word wrap algorithm。我的程序包含要包装的段落数，最大行长度和输入文本。例如：

1
5
This is a test.

但是，在接收输入文本并运行算法后，我收到以下运行时错误：

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1
at DynamicProgramming.main(DynamicProgramming.java:74)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)

我是否有可能将上述代码从C ++转换为Java，或者是否存在导致此异常的逻辑错误？感谢。

import java.util.Scanner;

public class DynamicProgramming {
    static int P;
    static int M;
    static String[] inputLine;

    public static void printNeatly(int M, int[] inputLineLengths) {
        int n = inputLineLengths.length;
        double[][] extraSpaces = new double[n][n];
        double[][] lineCost = new double[n][n];
        double[] optimalTotalCost = new double[n];
        int[] optimizedLengths = new int[n];

        for (int i=1; i <= n; i++) {
            extraSpaces[i][i] = M - inputLineLengths[i-1];

            for (int j=i+1; j <= n; j++) {
                extraSpaces[i][j] = extraSpaces[i][j-1] - inputLineLengths[j-1] -1;
            }
        }

        for (int i=1; i<= n; i++) {
            for (int j=i; j <=n; j++) {
                if (extraSpaces[i][j] < 0) {
                    lineCost[i][j] = Double.POSITIVE_INFINITY;
                }
                else if (j == n && extraSpaces[i][j] >= 0) {
                    lineCost[i][j] = 0;
                }
                else {
                    lineCost[i][j] = extraSpaces[i][j]*extraSpaces[i][j];
                }
            }
        }

        optimalTotalCost[0] = 0;
        for (int j=1; j <= n; j++) {
            optimalTotalCost[j] = Double.POSITIVE_INFINITY;

            for (int i=0; i <= j; i++) {
                if (optimalTotalCost[i-1] != Double.POSITIVE_INFINITY && lineCost[i][j] != Double.POSITIVE_INFINITY &&
                        (optimalTotalCost[i-1] + lineCost[i][j] < optimalTotalCost[j])) {
                    optimalTotalCost[j] = optimalTotalCost[i-1] + lineCost[i][j];
                    optimizedLengths[j] = i;
                }
            }
        }
    }

    public int printOutput(int[] optimizedLengths, int n) {
        int k;

        if (optimizedLengths[n] == 1) {
            k = 1;
        }
        else {
            k = printOutput(optimizedLengths, optimizedLengths[n]-1);
        }

        System.out.println(optimizedLengths[n]);
        return k;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        P = Integer.parseInt(scanner.nextLine());
        int[] inputLineLengths = new int[]{};


        for (int i=1; i <= P; i++) {
            M = Integer.parseInt(scanner.nextLine());
            inputLine = scanner.nextLine().split("[ ]+");
            inputLineLengths[i] = inputLine.length;
            printNeatly(M, inputLineLengths);
        }
    }
}

Answer 1

只需查看printNeatly方法：

你得到这样的数组的长度：

int n = inputLineLengths.length;

但是在你的循环中，你可以选择n：

for (int i=1; i <= n; i++) {

你需要在之前停止，因为数组（在Java中）从0索引到n-1（因此你很可能意味着从{{{{{{{{ 1}}，而不是0）

Answer 2

首先，您的inputLineLengths数组初始化为0长度，因此您无法将任何内容放入数组中。

首先将其初始化为P长度。

int[] inputLineLengths = new int[P];

其次，您的for循环需要覆盖有效索引值，范围从0到array's length - 1。将您的for循环更改为：

for (int i = 0; i < P; i++) {

for之外的其他main循环需要进行类似的更改。

需要帮助修复java.lang.ArrayIndexOutOfBoundsException

2 个答案: