前言：教授设定的指南，我必须使用数组，而不是其他一些数据结构。他的psuedo代码（不是很简洁）我们应该遵循的方法：
name and grade are read into a temporary location
loop from the end of the filled part of the array down to beginning {
if (new last name < current last name) {
copy current name and grade down
}
else if (new/current last names are equal and new first name < current first name) {
copy/assign current name and grade down
}
else {
found right place, break out of loop
}
}
now that you've made room, insert (copy) new name into correct sorted position
我看到我可能通过尝试读取数组位置[-1]来打破数组边界但是我想不出一种避免这种情况的方法，因为我从我拥有的项目数量向后计数比较它们。
我正在从文本文件中读取行并将每行的各个部分存储到结构中。然后我使用insert-sort-esque算法按字母顺序存储结构。但是，我的数组似乎没有填充前几行，新行只是覆盖了前面的行......就好像我的一个比较测试失败了，因为我的复制位置似乎永远不会改变，尽管这可能是因为初始数组填充以某种方式失败。我觉得很愚蠢，我一定会错过一些简单的东西......而且我的DisplayList模块显然永远不会得到一个已填充任何内容的数组。我是以不正确的方式改变阵列吗？
以下是带有问题的模块：
bool sortInput(ifstream &infile, StudentType students[], int size)
{
StudentType temp;
int copyToHere;
if(size == 0)
{
infile >> temp.last >> temp.first >> temp.grade;
strcpy(students[0].last, temp.last);
strcpy(students[0].first, temp.first);
students[0].grade = temp.grade;
size++;
}
while(infile)
{
infile >> temp.last >> temp.first >> temp.grade;
//cout << "TEST" << temp.last << temp.first << temp.grade << endl;
for(int i = size; i > 0; i--)
{
if(strcmp(temp.last, students[i-1].last) < 0)
{
students[i] = students[i-1];
students[i-1] = temp;
}
else if(strcmp(temp.last, students[i].last) == 0 && strcmp(temp.first, students[i].first) < 0)
{
students[i] = students[i-1];
}
else
{
break;
}
copyToHere = i;
}
cout << "Size = " << size << " and copy position = " << copyToHere << endl;
students[copyToHere] = temp;
size++;
//test to see if array is populated properly
for(int i = 0; i < size; i++)
{
cout << "Name is " << students[i].first << " " << students[i].last << " and grade is " << students[i].grade << endl;
}
cout << "DONE" << endl;
} //end while loop
return true;
}
以下是完整代码（如果需要，无论出于何种原因或进一步的背景）：
// ----------------------------------------------------------------------------
// You write meaningful doxygen comments and assumptions
#include <string.h>
#include <iostream>
#include <iomanip>
#include <fstream>
using namespace std;
int const MAXSIZE = 100; // maximum number of records in total
int const MAXLENGTH = 31; // maximum string length
int const MAXGRADE = 100; // highest possible grade
int const LOWGRADE = 0; // lowest possible grade
int const GROUP = 10; // group amount
int const HISTOGRAMSIZE = (MAXGRADE-LOWGRADE)/GROUP + 1; // grouped by GROUP
struct StudentType { // information of one student
int grade; // the grade of the student
char last[MAXLENGTH]; // last name (MAXLENGTH-1 at most)
char first[MAXLENGTH]; // first name (MAXLENGTH-1 at most)
};
// prototypes go here
bool sortInput(ifstream &, StudentType [], int);
void displayList(StudentType [], int);
/*setHistrogram();
displayHistogram();
findAverage();*/
//------------------------------- main ----------------------------------------
int main() {
StudentType students[MAXSIZE]; // list of MAXSIZE number of students
int size = 0; // total number of students
int histogram[HISTOGRAMSIZE]; // grades grouped by GROUP
int average = 0; // average exam score, truncated
// creates file object and opens the data file
ifstream infile("data1.txt");
if (!infile) {
cout << "File could not be opened." << endl;
return 1;
}
// read and sort input by last then first name
bool successfulRead = sortInput(infile, students, size);
// display list, histogram, and class average
if (successfulRead) {
displayList(students, size);
// setHistogram(... you figure parameters ...);
// displayHistogram(... you figure parameters ...);
// average = findAverage(... you figure parameters ...);
cout << "Average grade: " << average << endl << endl;
}
return 0;
}
bool sortInput(ifstream &infile, StudentType students[], int size)
{
StudentType temp;
int copyToHere;
if(size == 0)
{
infile >> temp.last >> temp.first >> temp.grade;
strcpy(students[0].last, temp.last);
strcpy(students[0].first, temp.first);
students[0].grade = temp.grade;
size++;
}
while(infile)
{
infile >> temp.last >> temp.first >> temp.grade;
//cout << "TEST" << temp.last << temp.first << temp.grade << endl;
for(int i = size; i > 0; i--)
{
if(strcmp(temp.last, students[i-1].last) < 0)
{
students[i] = students[i-1];
students[i-1] = temp;
}
else if(strcmp(temp.last, students[i].last) == 0 && strcmp(temp.first, students[i].first) < 0)
{
students[i] = students[i-1];
}
else
{
break;
}
copyToHere = i;
}
cout << "Size = " << size << " and copy position = " << copyToHere << endl;
students[copyToHere] = temp;
size++;
//test to see if array is populated properly
for(int i = 0; i < size; i++)
{
cout << "Name is " << students[i].first << " " << students[i].last << " and grade is " << students[i].grade << endl;
}
cout << "DONE" << endl;
} //end while loop
return true;
}
void displayList(StudentType students[], int size)
{
cout << "List of names sorted:" << endl;
for(int i = 0; i < size; i++)
{
cout << " " << students[i].grade << " " << students[i].last << " " << students[i].first << endl;
}
}
// ----------------------------------------------------------------------------
// functions with meaningful doxygen comments and assumptions go here
答案 0 :(得分：1)
您的插入排序并未正确插入。让我们看一下主插入循环的一部分：
if(strcmp(temp.last, students[i-1].last) < 0)
{
students[i] = students[i-1];
students[i-1] = temp;
}
这意味着将temp插入位置i-1的数组中。您正在将项目转移到i-1到i，但是数组中的其他元素发生了什么变化？您需要将它们全部向上移动一个位置，以便为插入的元素腾出空间。类似的东西：
memmove(students + i, students + i - 1, sizeof(students[0]) * size - i - 1);
您的代码中也存在其他问题。 copyToHere可能未初始化。您正在多次将temp复制到数组中（students[i-1] = temp;并且students[copyToHere] = temp;都不是必需的。一旦你完成了内循环的插入，你应该突破。当列表为空时，您的特殊处理并不是必需的，等等。
查看pseudo-code for an insertion sort algorithm并查看是否可以简化和重写您的问题以消除问题。
答案 1 :(得分：0)
解决我自己的问题哈哈。我没有完全正确完成其他声明，这是愚蠢的。现在我正在努力重做我的名字比较，因为它不会按字母顺序排列相同的姓氏。
经验教训：在认为你被分叉之前，先把它弄得一团糟。现在我真的觉得自己像个白痴，希望不要浪费很多时间。
for(int i = size; i > 0; i--)
{
if(strcmp(temp.last, students[i-1].last) < 0)
{
students[i] = students[i-1];
students[i-1] = temp;
}
else if(strcmp(temp.last, students[i].last) == 0 && strcmp(temp.first, students[i].first) < 0)
{
students[i] = students[i-1];
students[i-1] = temp;
}
else
{
students[i] = temp;
break;
}
insertHere = i;
}