第三次作业参考答案

一、实现一个重载的max()函数，让它接受以下参数：（a）两个整数；（b）两个浮点数；（c）两个字符串；（d）一个整数vector;  (e) 一个浮点数vector; (f) 一个字符串vector; (g)一个整数数组， 以及一个表示数组大小的整数值：(h) 一个浮点数数组，以及一个表示数组大小的整数值：（i）一个字符串数组，以及一个表示数组大小的整数值。最后，撰写main()测试这些函数。

#include <iostream>
#include <vector>
#include <string>

using namespace std;

int max(int, int);
double max(double, double);
string max(string, string);
int max(vector<int>);
double max(vector<double>);
string max(vector<string>);
int max(int *, int);
double max(double *, int);
string max(string *, int);

int main()
{
cout << "Please enter 2 integers:" << endl;
int ix , iy;
cin >> ix >> iy;
cout << max(ix, iy) << endl;

cout << "Please enter 2 floats:" << endl;
double fx, fy;
cin >> fx >> fy;
cout << max(fx, fy) << endl;

cout << "Please enter 2 strings:" << endl;
string sx, sy;
cin >> sx >> sy;
cout << max(sx, sy) <<endl;

int n;

cout << "Please enter the length of a vector:" << endl;
cin >> n;
cout << "Please enter " << n << " integers:" << endl;
vector<int> iv;
for (int i = 0; i < n; i ++)
{
int x;
cin >> x;
iv.push_back(x);
}
cout << max(iv) << endl;

cout << "Please enter the length of a vector:" << endl;
cin >> n;
cout << "Please enter " << n << " floats:" << endl;
vector<double> fv;
for (int i = 0; i < n; i ++)
{
double x;
cin >> x;
fv.push_back(x);
}
cout << max(fv) << endl;

cout << "Please enter the length of a vector:" << endl;
cin >> n;
cout << "Please enter " << n << " strings:" << endl;
vector<string> sv;
for (int i = 0; i < n; i ++)
{
string x;
cin >> x;
sv.push_back(x);
}
cout << max(sv) << endl;

cout << "Please enter the length of an array:" << endl;
cin >> n;
cout << "Please enter " << n << " integers:" << endl;
int *ia = new int
;
for (int i = 0; i < n; i ++)
cin >> ia[i];
cout << max(ia, n) << endl;
delete ia;

cout << "Please enter the length of an array:" << endl;
cin >> n;
cout << "Please enter " << n << " floats:" << endl;
double *fa = new double
;
for (int i = 0; i < n; i ++)
cin >> fa[i];
cout << max(fa, n) << endl;
delete fa;

cout << "Please enter the length of an array:" << endl;
cin >> n;
cout << "Please enter " << n << " strings:" << endl;
string *sa = new string
;
for (int i = 0; i < n; i ++)
cin >> sa[i];
cout << max(sa, n) << endl;
delete sa;

return 0;
}

int max(int v1, int v2)
{
return v1 > v2 ? v1 : v2;
}

double max(double v1, double v2)
{
return v1 > v2 ? v1 : v2;
}

string max(string v1, string v2)
{
return v1 > v2 ? v1 : v2;
}

int max(vector<int> ivec)
{
int tmp = ivec[0];
for (int ix = 1; ix < ivec.size(); ix ++)
if (ivec[ix] > tmp) tmp = ivec[ix];
return tmp;
}

double max(vector<double> ivec)
{
double tmp = ivec[0];
for (int ix = 1; ix < ivec.size(); ix ++)
if (ivec[ix] > tmp) tmp = ivec[ix];
return tmp;
}

string max(vector<string> ivec)
{
string tmp = ivec[0];
for (int ix = 1; ix < ivec.size(); ix ++)
if (ivec[ix] > tmp) tmp = ivec[ix];
return tmp;
}

int max(int *arr, int size)
{
int tmp = arr[0];
for (int i = 1; i < size; i ++)
if (arr[i] > tmp) tmp = arr[i];
return tmp;
}

double max(double *arr, int size)
{
double tmp = arr[0];
for (int i = 1; i < size; i ++)
if (arr[i] > tmp) tmp = arr[i];
return tmp;
}
string max(string *arr, int size)
{
string tmp = arr[0];
for (int i = 1; i < size; i ++)
if (arr[i] > tmp) tmp = arr[i];
return tmp;
}

二、以template重新完成试题一，并对main()函数做适度的修改。

#include <iostream>
#include <vector>
#include <string>

using namespace std;

template <typename T>
T Max(T v1, T v2)
{
return v1 > v2 ? v1 : v2;
}

template <typename T>
T Max(vector<T> v)
{
T max = v[0];
for (int ix = 1; ix < v.size(); ix ++)
if (v[ix] > max)
max = v[ix];
return max;
}

template <typename T>
T Max(T *v, int size)
{
T max = v[0];
for (int ix = 1; ix < size; ix ++)
if (v[ix] > max) max = v[ix];
return max;
}

int main()
{
cout << "Please enter 2 integers:" << endl;
int ix , iy;
cin >> ix >> iy;
cout << Max(ix, iy) << endl;

cout << "Please enter 2 floats:" << endl;
double fx, fy;
cin >> fx >> fy;
cout << Max(fx, fy) << endl;

cout << "Please enter 2 strings:" << endl;
string sx, sy;
cin >> sx >> sy;
cout << Max(sx, sy) <<endl;

int n;

cout << "Please enter the length of a vector:" << endl;
cin >> n;
cout << "Please enter " << n << " integers:" << endl;
vector<int> iv;
for (int i = 0; i < n; i ++)
{
int x;
cin >> x;
iv.push_back(x);
}
cout << Max(iv) << endl;

cout << "Please enter the length of a vector:" << endl;
cin >> n;
cout << "Please enter " << n << " floats:" << endl;
vector<double> fv;
for (int i = 0; i < n; i ++)
{
double x;
cin >> x;
fv.push_back(x);
}
cout << Max(fv) << endl;

cout << "Please enter the length of a vector:" << endl;
cin >> n;
cout << "Please enter " << n << " strings:" << endl;
vector<string> sv;
for (int i = 0; i < n; i ++)
{
string x;
cin >> x;
sv.push_back(x);
}
cout << Max(sv) << endl;

cout << "Please enter the length of an array:" << endl;
cin >> n;
cout << "Please enter " << n << " integers:" << endl;
int *ia = new int
;
for (int i = 0; i < n; i ++)
cin >> ia[i];
cout << Max(ia, n) << endl;
delete ia;

cout << "Please enter the length of an array:" << endl;
cin >> n;
cout << "Please enter " << n << " floats:" << endl;
double *fa = new double
;
for (int i = 0; i < n; i ++)
cin >> fa[i];
cout << Max(fa, n) << endl;
delete fa;

cout << "Please enter the length of an array:" << endl;
cin >> n;
cout << "Please enter " << n << " strings:" << endl;
string *sa = new string
;
for (int i = 0; i < n; i ++)
cin >> sa[i];
cout << Max(sa, n) << endl;
delete sa;

return 0;
}

三、定义三个数列，数列的求值公式分别是（1）a1=1, a2=1, an=an-1+2*an-2(n>=3)，（2）a1=1, an=an-1+2*n(n>=2)，（3）a1=1, an=an-1+n*n(n>=2)，根据以上三个数列的求值公式，定义一个通用函数，输入n值和数列序号，输出相应数列的an值，撰写main()，并测试该函数。

关于第三小题的说明：

1.大家不要因为学了static之后就到处乱用，要注意使用场合。

#include <iostream>
#include <vector>
using namespace std;

#define Maxn 3

typedef int (*fun_p) (int);// 定义函数指针，下面用到了函数数组

int function1(int iPos)
{
if (iPos < 1 || iPos > 32)
{
cerr << "The length is not supported!" << endl;
return -1;
}
vector<int> ivec1;
for (int ix = ivec1.size(); ix < iPos; ix ++)
{
if (ix == 0 || ix == 1)
ivec1.push_back(1);
else
ivec1.push_back(ivec1[ix - 1] + 2 * ivec1[ix - 2]);
}
return ivec1[iPos - 1];
}

int function2(int iPos)
{
if (iPos < 1 || iPos > 46340)
{
cerr << "The length is not supported!" << endl;
return -1;
}
vector<int> ivec2;
for (int ix = ivec2.size(); ix < iPos; ix ++)
{
if (ix == 0)
ivec2.push_back(1);
else
ivec2.push_back(ivec2[ix - 1] + 2 * (ix + 1));
}
return ivec2[iPos - 1];
}

int function3(int iPos)
{
if (iPos < 1 || iPos > 1860)
{
cerr << "The length is not supported!" << endl;
return -1;
}
a81d
vector<int> ivec3;
for (int ix = ivec3.size(); ix < iPos; ix ++)
{
if (ix == 0)
ivec3.push_back(1);
else
ivec3.push_back(ivec3[ix - 1] + (ix + 1) * (ix + 1));
}
return ivec3[iPos - 1];
}

//post:根据数列编号和这个数在数列中的位置计算出这个数
int seqs(int iPos, int order, int &iNum)
{
//0 means there is not such an order
//-1 means the length of the order is not supported
//>0 means exit successfully
if (order < 1 || order > 3)
{
iNum = 0;
return 0;
}
//函数指针数组，具体了解请google
const fun_p fp[Maxn] = {function1, function2, function3};
iNum = fp[order - 1](iPos);
return iNum;
}

int main()
{
int iPos, order, iNum;
while (true)
{
cin >> iPos >> order;
int sign = seqs(iPos, order, iNum);
if (sign > 0)
cout << iNum << endl;
else
if (sign == 0)
cerr << "There is not such an order!" << endl;
}
return 0;
}