Question

我一直在尝试进行合并排序，将字符串数组和int数组排序在一起。 int [0]指向word [0]所以当word [0]转换为word [2]时，int [0]也应该转换为int [2]。但是，我的输出是不同的： A B C D 4 3 1 3。我做错了什么？

public static void main(String[] args) {
    String[] word = {"c", "b", "d", "a"};
    int[] lineNumber = {1, 2, 3, 4};
    mergeSort(word, lineNumber, 0, word.length-1);
    for(int i = 0; i< word.length; i++) {
        System.out.print(word[i] + " ");
    }
    System.out.println();
    for(int i =0; i < word.length; i++)
        System.out.print(lineNumber[i] + " ");
}



static void mergeSort(String[] word, int[] lineNumber, int p, int r) {
    int q;
    if(p < r) {
        q = (p+r)/2;
        mergeSort(word, lineNumber, p, q);
        mergeSort(word, lineNumber, q+1, r);
        merge(word, lineNumber, p, q, r);
    }
}

static void merge(String[] word, int[] lineNumber, int p, int q, int r) {
    int n1 = q-p+1;
    int n2 = r-q;
    String[] lWord = new String[n1];
    String[] rWord = new String[n2];
    int[] lLineNum = new int[n1];
    int[] rLineNum = new int[n2];
    int i, j, k;

    for(i=0; i<n1; i++) {
        lWord[i] = word[p+i];
        lLineNum[i] = lineNumber[p+i];
    }

    for(j=0; j<n2; j++) {
        rWord[j] = word[q+j+1];
        rLineNum[j] = lineNumber[q+j+1];
    }

    i = 0; j = 0;
    for(k=p; k<=r; k++) {
        if(i<n1 && j<n2) {
            if(lWord[i].compareTo(rWord[j]) < 0) {
                word[k] = lWord[i];
                lineNumber[k] = lLineNum[i];
                i++;
            }else 
                word[k] = rWord[j];
                lineNumber[k] = rLineNum[j];
                j++;
            }
            else if(i<n1) {
                word[k] = lWord[i];
                lineNumber[k] = lLineNum[i];
                i++;
            }else if(j<n2){
                word[k] = rWord[j];
                lineNumber[k] = rLineNum[j];
                j++;
            }
    }
}

Answer 1

问题出在merge。它应该是这样的：

static void merge(String[] word, int[] lineNumber, int p, int q, int r) {
    int n1 = q-p+1;
    int n2 = r-q;
    String[] lWord = new String[n1];
    String[] rWord = new String[n2];
    int[] lLineNum = new int[n1];
    int[] rLineNum = new int[n2];
    int i, j, k;

    for(i=0; i<n1; i++) {
        lWord[i] = word[p+i];
        lLineNum[i] = lineNumber[p+i];
    }

    for(j=0; j<n2; j++) {
        rWord[j] = word[q+j+1];
        rLineNum[j] = lineNumber[q+j+1];
    }

    i = 0; j = 0;
    for(k=p; k<=r; k++) {
        if(i<n1 && j<n2) {
            if(lWord[i].compareTo(rWord[j]) < 0) {
                word[k] = lWord[i];
                lineNumber[k] = lLineNum[i];
                i++;
            }else {
                word[k] = rWord[j];
                lineNumber[k] = rLineNum[j];
                j++;
            }
        } else if(i<n1) {
            word[k] = lWord[i];
            lineNumber[k] = lLineNum[i];
            i++;
        } else if(j<n2){
            word[k] = rWord[j];
            lineNumber[k] = rLineNum[j];
            j++;
        }
    }
}

问题在于if-else。它们在代码中的结构不正确，看起来非常像（在修复缩进后）：

if(i<n1 && j<n2) {
    if(lWord[i].compareTo(rWord[j]) < 0) {
        word[k] = lWord[i];
        lineNumber[k] = lLineNum[i];
        i++;
    }else // HERE next 3 lines should be in a {} block
        word[k] = rWord[j];
    lineNumber[k] = rLineNum[j];
    j++;
}
else if(i<n1) {
    word[k] = lWord[i];
    lineNumber[k] = lLineNum[i];
    i++;
}else if(j<n2){
    word[k] = rWord[j];
    lineNumber[k] = rLineNum[j];
    j++;
}

在我看来，如果不使用两个数组（int []和String []），代码会更清晰，你可以使用包含word和lineNo的类的单个数组。类似的东西：

public class WordAndPosition {
  public String word;
  public int lineNo;
}

WordAndPosition[]

合并排序字符串数组和int数组java

1 个答案: