[英]C++ Bubble sort dynamically allocated array
我编写了一个冒泡排序算法,该算法使用字符串比较对动态分配的数组进行排序。
这是我的代码:
void AddressBook::bubble_sort_address_book(){
bool swapped = true;
while(swapped){
swapped = false;
for(int i = 0; i < noOfEmployees; i++){
if(employees[i].combined_name() > employees[i+1].combined_name()){
Employee temp_employee = employees[i+1];
employees[i+1] = employees[i];
employees[i] = temp_employee;
}
}
}
}
我的问题很明显,但我似乎仍无法弄清楚如何解决它:代码有时会在网上失败(以未定义的方式):
Employee temp_employee = employees[i+1]
这非常明显,因为如果i
等于数组的末尾,则使用i+1
访问内存将导致未定义的行为。 但是,如果我使用noOfEmployees-1
停止for循环,则不会发生,但第一个元素永远不会排序(很明显)。
如何正确实施冒泡排序? 这似乎是一件微不足道的任务。 我想念什么吗?
纯C中的以下简化版本可以正常工作:
int employees[10]= {3,1,7,6,9,7,1,0,2,6};
int noOfEmployees= 10;
void bubble_sort_address_book(void){
bool swapped = true;
int i;
while(swapped){
swapped = false;
for(i = 0; i < noOfEmployees-1; i++){
if(employees[i] > employees[i+1]){
int temp_employee = employees[i+1];
employees[i+1] = employees[i];
employees[i] = temp_employee;
swapped= true;
}
}
}
}
int main()
{
int i;
bubble_sort_address_book();
for (i=0; i<noOfEmployees; i++) {
printf("emp %d= %d\n", i, employees[i]);
}
return 0;
}
根据您的要求,变量swapped
的功能是指示在完全通过数组之后没有发生交换,因此它表明该数组现在已排序。
您可以在外部循环上使用显式绑定。
您还应该将事情分解为较小的功能。
bool operator <(Employee const & lhs, Employee const & rhs) {
return lhs.combined_name() < rhs.combined_name();
}
// a.k.a. std::swap
void swap(Employee & lhs, Employee & rhs) {
Employee temp(static_cast<Employee&&>(lhs)); // a.k.a. std::move
lhs = static_cast<Employee&&>(rhs);
rhs = static_cast<Employee&&>(temp);
}
void bubble_sort_impl(Employee * begin, Employee * end) {
for (; end != begin; --end) {
for (Employee * it = begin; it+1 != end; ++it) {
if (*(it+1) < *it) {
swap(*it, *(it+1));
}
}
}
}
// do we really need "bubble_" or "_address_book" in this name?
void AddressBook::bubble_sort_address_book() {
bubble_sort_impl(employees, employees + noOfEmployees);
}
另一个解决方案:
#include <iostream>
#include <vector>
using namespace std;
int employees[10] = { 3,1,7,6,9,7,1,0,2,6 };
void bubble_sort_address_book(void) {
bool swapped = true;
int i;
int noOfEmployees = 10;
while (swapped) {
swapped = false;
for (i = 1; i <= noOfEmployees ; i++) {
if (employees[i] > employees[i - 1]) {
int temp_employee = employees[i - 1];
employees[i - 1] = employees[i];
employees[i] = temp_employee;
swapped = true;
}
}
}
}
int main()
{
int i;
int noOfEmployees = 10;
bubble_sort_address_book();
for (i = 0; i<noOfEmployees; i++) {
printf("emp %d= %d\n", i, employees[i]);
}
return 0;
}
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.