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[n];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[n];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[n];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[n];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[n];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[n];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, a_n=a_n-1+2*a_n-2(n>=3)，（2）a₁=1, a_n=a_n-1+2*n(n>=2)，（3）a₁=1, a_n=a_n-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a_n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 3typedef 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;    }    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;}