笔试面试相关记录（8）
（1）
#include
using namespace std;
class A {
private:
int a1 = 0;
public:
A() {}
A(const A& a) {
// cout << "A(const A& a)" << endl;
// this->a1 = a.a1;
}
A operator++(int) {
A T = *this;
a1++;
cout << "++(int)" << " " << this->a1 << " " << T.a1 << endl;
return T;
}
A& operator++() {
A T = *this;
a1++;
cout << "++()" << " " << this->a1 << " " << T.a1 << endl;
return *this;
}
A& operator=(const A& a) {
cout << "=(const A& a)" << endl;
this->a1 = a.a1;
}
void print() {cout << a1 << " "<< this->a1 << endl;}
};
int main()
{
A obj;
// 调用++()，返回*this&,输出1,在A T = *this时会调用拷贝构造函数，但是
// 拷贝构造函数中并没有任何操作，所以T.a1 = 0, 返回*this对象调用print()，输出1 1
(++obj).print();
// 调用++(int),返回T，此时a1=2，A T = *this时会调用拷贝构造函数，但是
// 拷贝构造函数中并没有任何操作，所以T.a1 = 0,输出++(int) 2 0
obj++;
// 输出2 2
obj.print();
// 调用++(int)，T.a1 = 0, 输出++(int) 3 0，返回T，调用print输出0 0
(obj++).print();
// 调用++(),T.a1 = 0,输出++() 4 0，返回*this,调用print输出4 4
(++obj).print();
return 0;
}
输出：
++() 1 0
1 1
++(int) 2 0
2 2
++(int) 3 0
0 0
++() 4 0
4 4 （2）
#include
using namespace std;
class A {
private:
int a1 = 0;
public:
A() {}
A(const A& a) {
cout << "A(const A& a)" << endl;
this->a1 = a.a1;
}
A operator++(int) {
A T = *this;
a1++;
cout << "++(int)" << " " << this->a1 << " " << T.a1 << endl;
return T;
}
A& operator++() {
A T = *this;
a1++;
cout << "++()" << " " << this->a1 << " " << T.a1 << endl;
return *this;
}
A& operator=(const A& a) {
cout << "=(const A& a)" << endl;
this->a1 = a.a1;
}
void print() {cout << a1 << " "<< this->a1 << endl;}
};
int main()
{
A obj;
// 调用++()，返回*this&,输出1,在A T = *this时会调用拷贝构造函数，
// 所以T.a1 = 0, a1++, 返回*this对象调用print()，输出1 1
(++obj).print();
// 调用++(int),返回T，此时a1=2，A T = *this时会调用拷贝构造函数，
// T.a1 = 1,输出++(int) 2 1
obj++;
// 输出2 2
obj.print();
// 调用++(int)，T.a1 = 2, 输出++(int) 3 2，返回T，调用print输出2 2
(obj++).print();
// 调用++(),T.a1 = 3,输出++() 4 3，返回*this,调用print输出4 4
(++obj).print();
return 0;
}
输出：
A(const A& a)
++() 1 0
1 1
A(const A& a)
++(int) 2 1
2 2
A(const A& a)
++(int) 3 2
2 2
A(const A& a)
++() 4 3
4 4 （3）用两个栈来实现双端队列
#include
#include
#include
using namespace std;
class MyDeque {
public:
void push_back(int num) {
stk1.push(num);
size++;
}
void push_front(int num) {
while (stk1.size()) {
int t = stk1.top();
stk2.push(t);
stk1.pop();
}
stk1.push(num);
while (stk2.size()) {
int t = stk2.top();
stk1.push(t);
stk2.pop();
}
size++;
}
int pop_front() {
while (stk1.size()) {
int t = stk1.top();
stk2.push(t);
stk1.pop();
}
int res = stk2.top();
stk2.pop();
while (stk2.size()) {
int t = stk2.top();
stk1.push(t);
stk2.pop();
}
size--;
return res;
}
int pop_back() {
int res = stk1.top();
stk1.pop();
size--;
return res;
}
bool empty() const {
return size == 0;
}
private:
stack stk1, stk2;
int size = 0;
};
int main() {
string str;
while (getline(cin, str)) {
MyDeque mydeque;
int len = str.size();
int i = 0;
// F1 F2 F3 F4 F5 B1 B2 B3 B4 B5 PF PF PB PB
while (i < len) {
if (str[i] == 'F') {
int j = i+1;
int num = 0;
while (str[j] != ' ') {
num = num*10 + (str[j]-'0');
j++;
}
mydeque.push_front(num);
i = j+1;
} else if (str[i] == 'B') {
int j = i+1;
int num = 0;
while (str[j] != ' ') {
num = num*10 + (str[j] - '0');
j++;
}
mydeque.push_back(num);
i = j+1;
} else if (str[i] == 'P' && str[i+1] == 'F') {
cout << mydeque.pop_front() << " ";
i += 2;
} else if (str[i] == 'P' && str[i+1] == 'B') {
cout << mydeque.pop_back() << " ";
i += 2;
} else if (str[i] == ' ') {
i++;
}
}
}
} （4）找两个有序数组的中位数
输入：
// a : [1, 3, 5]
// b: [2, 4, 6]
#include
#include
#include
using namespace std;
// a : [1, 3, 5]
// b: [2, 4, 6]
vector getVector(string str) {
int len = str.size();
vector ans;
int t = 0;
for (int i = 0; i < len; i++) {
if (isdigit(str[i])) {
t = t*10 + (str[i]-'0');
} else if (str[i] == ',') {
ans.push_back(t);
t = 0;
}
}
ans.push_back(t);
return ans;
}
int main() {
string str1, str2;
while (getline(cin, str1)) { // 注意 while 处理多个 case
getline(cin, str2);
vector num1 = getVector(str1);
vector num2 = getVector(str2);
// for (int i = 0; i < num1.size(); i++) {
// cout << num1[i] << " - ";
// }
// cout << endl;
// for (int i = 0; i < num2.size(); i++) {
// cout << num2[i] << " = ";
// }
int n = num1.size();
vector total(2*n);
int i = 0, j = 0, k = 0;
while (i < n && j < n) {
if (num1[i] < num2[j]) {
total[k++] = num1[i++];
} else {
total[k++] = num2[j++];
}
}
while (i < n) {
total[k++] = num1[i++];
}
while (j < n) {
total[k++] = num2[j++];
}
cout << float(total[n-1] + total[n]) / 2 << endl;
}
} （5）
#include
using namespace std;
int main()
{
int a = 5;
a += a*= a%= 3;
cout << a;
return 0;
}
输出: 8 (6)
#include
using namespace std;
int main()
{
int a = 1;
int b = 2;
// auto f = [a, &b]()->int{return a+ ++b;};
// int c = f();
// cout << b;
cout << a+ ++b << " " << a << " " << b << endl;
a = 1;
b = 2;
cout << a+++b << " " << a << " " << b << endl;
a = 1;
b = 2;
cout << a++ +b << " " << a << " " << b << endl;
return 0;
}
输出:
4 1 3
3 2 2
3 2 2 #include
using namespace std;
int main()
{
int a = 1;
int b = 2;
auto f = [a, &b]()->int{return a+ ++b;};
int c = f();
cout << b;
return 0;
}
输出：3 #include
using namespace std;
int main()
{
int a = 1;
int b = 2;
auto f = [a, &b]()->int{return a+++b;};
int c = f();
cout << b;
return 0;
}
编译报错 #include
using namespace std;
int main()
{
int a = 1;
int b = 2;
auto f = [&]()->int{return a+++b;};
int c = f();
cout << a << " " << b;
return 0;
}
输出：2 2 #include
using namespace std;
int main()
{
int a = 1;
int b = 2;
auto f = [&]()->int{return a+ ++b;};
int c = f();
cout << a << " " << b;
return 0;
}
输出：1 3 #include
using namespace std;
int main()
{
printf("%lld", long((int*)(0)+1) - long((int*)(0)));
return 0;
}
输出:4