int num=2,i=3;while(--i);{i--;num++;}cout<<num<<endl;
时间: 2023-05-23 21:06:53 浏览: 25
A:输出结果是2。在这段代码中,先执行了while(--i),这会让i减1直到等于0,循环结束后i的值为0,然后继续执行{...}中的语句,即i--和num,这时i的值变成了-1,num的值还是2,最后执行cout<<num<<endl;输出2。
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把这段代码翻译成java语言(源语言为c++)#include <iostream> #include <cmath> using namespace std; bool isPerfectSquare(int num) { for(int i = 1; i * i <= num; i++) { if(i * i == num) { return true; } } return false; } int main() { int num = 0; for(int i = 1000; i <= 9999; i++) { int t = 0; int p = i; while(p != 0) { int x= p % 10; t = t * 10 + x; p /= 10; } if(isPerfectSquare(abs(t - i))) { num++; } } cout << num; return 0; }
以下是将C++代码翻译成Java的代码:
import java.lang.Math;
public class Main {
public static boolean isPerfectSquare(int num) {
for(int i = 1; i * i <= num; i++) {
if(i * i == num) {
return true;
}
}
return false;
}
public static void main(String[] args) {
int num = 0;
for(int i = 1000; i <= 9999; i++) {
int t = 0;
int p = i;
while(p != 0) {
int x = p % 10;
t = t * 10 + x;
p /= 10;
}
if(isPerfectSquare(Math.abs(t - i))) {
num++;
}
}
System.out.println(num);
}
}
void LookupNum(Student stu[]) { system("cls"); int n = Read(stu); int s; int i = 0; cout << endl << "======>> 查找学生成绩 <<======" << endl; cout << "请输入要查找学生的学号:"; cin >> s; while ((stu[i].num - s) != 0 && i < n)i++; if (i == n) { cout << "======>> 对不起,无法找到该学生...... <<======" << endl; } else { cout << "----------------------------" << endl; cout << "班级:" << stu[i].class_0 << endl; cout << "学号:" << stu[i].num << endl; cout << "姓名:" << stu[i].name << endl; cout << "电子技术:" << stu[i].elec << endl; cout << "C++程序设计:" << stu[i].c_program << endl; cout << "多媒体技术:" << stu[i].media << endl; cout << "大学英语:" << stu[i].english << endl; cout << "高等数学:" << stu[i].math << endl; cout << "大学体育:" << stu[i].sport << endl; cout << "马克思主义基本原理:" << stu[i].polity << endl; cout << "平均分:" << stu[i].average << endl; cout << "总分:" << stu[i].total << endl; } }修改为折半查找
折半查找(也称二分查找)需要一个有序数组,先比较数组中间位置的元素和目标元素的大小关系,如果相等则直接返回下标,否则根据大小关系缩小查找范围并继续查找。因此,需要对stu数组进行排序,可以使用STL中的sort函数进行升序排序,然后使用二分查找算法进行查找。
修改后的代码如下:
```
void LookupNum(Student stu[]) {
system("cls");
int n = Read(stu);
int s;
cout << endl << "======>> 查找学生成绩 <<======" << endl;
cout << "请输入要查找学生的学号:";
cin >> s;
// 先对stu数组按学号升序排序
sort(stu, stu + n, [](const Student& a, const Student& b) { return a.num < b.num; });
// 二分查找目标学号
int left = 0, right = n - 1;
while (left <= right) {
int mid = (left + right) / 2;
if (stu[mid].num == s) {
cout << "----------------------------" << endl;
cout << "班级:" << stu[mid].class_0 << endl;
cout << "学号:" << stu[mid].num << endl;
cout << "姓名:" << stu[mid].name << endl;
cout << "电子技术:" << stu[mid].elec << endl;
cout << "C++程序设计:" << stu[mid].c_program << endl;
cout << "多媒体技术:" << stu[mid].media << endl;
cout << "大学英语:" << stu[mid].english << endl;
cout << "高等数学:" << stu[mid].math << endl;
cout << "大学体育:" << stu[mid].sport << endl;
cout << "马克思主义基本原理:" << stu[mid].polity << endl;
cout << "平均分:" << stu[mid].average << endl;
cout << "总分:" << stu[mid].total << endl;
return; // 直接返回
} else if (stu[mid].num < s) {
left = mid + 1;
} else {
right = mid - 1;
}
}
cout << "======>> 对不起,无法找到该学生...... <<======" << endl;
}
```
需要注意的是,折半查找要求数组有序,因此在查找之前需要对stu数组按学号升序排序。另外,如果找到目标学生,直接返回即可,不需要继续查找。