C++Primer第五版——习题答案详解（八）

其他 2019-03-15 18:01:21 阅读次数: 0

习题答案目录：https://www.cnblogs.com/Mered1th/p/10485695.html

第9章 顺序容器

练习9.1
a.list，需要按字典序插入，可能插入位置在中间
b.deque，需要在头部和尾部操作
c.vector

练习9.2

list<deque<int>> li;

练习9.4

bool findInt(vector<int> &vec, int x) {
    for (auto i : vec) {
        if (i == x) {
            return true;
        }
    }
    return false;
}

练习9.5

int findInt(vector<int> &vec, int x) {
    for (auto i : vec) {
        if (i == x) {
            return x;
        }
    }
    return -1;
}

练习9.6
改成 iter1!=iter2

练习9.7

vector<int>::size_type;

练习9.8

list<string>::const_iterator;
list<string>::iterator;

练习9.9
begin返回容器的iterator类型
cbegin返回容器的const_iterator类型

练习9.10

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

using namespace std;

int main() {
    list<int> li(5, 3);
    vector<int> ivec(5, 5);

    vector<double> dvec(li.begin(), li.end());
    for (auto i : dvec) {
        cout << i << " ";
    }
    cout << endl;

    vector<double> dvec2(ivec.begin(), ivec.end());
    for (auto i : dvec2) {
        cout << i << " ";
    }
    cout << endl;

    system("pause");
    return 0;
}

练习9.14

list<const char *> oldli = { "a","an","the" };
        vector<string> svec;
        svec.assign(oldli.begin(), oldli.end());

练习9.15

bool isEquel(vector<int> &a, vector<int> &b) {
    if (a == b) return true;
    else return false;
}

练习9.16

bool isEquel(vector<int> &a, list<int> &b) {
    vector<int> c(b.begin(), b.end());
    if (a == c) return true;
    else return false;
}

练习9.18

#include<iostream>
#include<string>
#include<deque>

using namespace std;

int main() {
    string s;
    deque<string> ans;
    while (cin >> s) {
        ans.push_back(s);
    }
    for (auto it = ans.begin();it != ans.end();++it) {
        cout << *it << endl;
    }
    system("pause");
    return 0;
}

练习9.19
将deque改为list即可。

#include<iostream>
#include<string>
#include<deque>
#include<list>

using namespace std;

int main() {
    string s;
    list<string> ans;
    while (cin >> s) {
        ans.push_back(s);
    }
    for (auto it = ans.begin();it != ans.end();++it) {
        cout << *it << endl;
    }
    system("pause");
    return 0;
}

练习9.20

#include<iostream>
#include<deque>
#include<list>

using namespace std;

int main() {
    list<int> ori = { 1,2,3,4,5,6 };
    deque<int> odd, even;
    for (auto i : ori) {
        if (i % 2) {
            even.push_back(i);
        }
        else {
            odd.push_back(i);
        }
    }
    for (auto i : odd) {
        cout << i << " ";
    }
    cout << endl;
    for (auto i : even) {
        cout << i << " ";
    }

    system("pause");
    return 0;
}

练习9.22

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

using namespace std;

void func(vector<int> &iv, int some_val) {
    int extra = 0;
    vector<int>::iterator iter = iv.begin();
    while (iter != (iv.begin() + iv.size() / 2 + extra)) {
        if (*iter == some_val) {
            iter = iv.insert(iter, 2 * some_val);
            ++extra;
            ++iter;
        }
        ++iter;
    }
}
int main() {
    vector<int> iv = { 1,2,3,4 };
    func(iv, 2);
    for (auto i : iv) {
        cout << i << " ";
    }
    system("pause");
    return 0;
}

练习9.24

#include<iostream>
#include<vector>

using namespace std;

int main() {
    vector<int> vec;
    int a = vec.at(0),
        b = vec[0],
        c = vec.front();
    auto d = vec.begin();
    cout << "a: " << a << endl;
    cout << "b: " << b << endl;
    cout << "c: " << c << endl;
    cout << "d: " << *d << endl;
    system("pause");
    return 0;
}

练习9.25
如果elem1与elem2相等，则一个元素都不会删除。
如果elem2是尾后迭代器，则会从elem1元素删除到最后一个元素。
如果elem1与elem2都是尾后迭代器，则一个元素都不会删除。

练习9.26

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

int main() {
    int ia[] = { 0,1,1,2,3,5,8,13,21,55,89 };
    vector<int> vec(ia, end(ia));
    list<int> li(ia, end(ia));
    for (auto it = li.begin(); it != li.end();) {
        if (*it % 2 == 1) {
            it = li.erase(it);
        }
        else {
            ++it;
        }
    }
    for (auto i : li) {
        cout << i << " ";
    }
    cout << endl;
    for (auto it = vec.begin();it != vec.end();) {
        if (*it % 2 == 0) {
            it = vec.erase(it);
        }
        else {
            ++it;
        }
    }
    for (auto i : vec) {
        cout << i << " ";
    }
    cout << endl;
    system("pause");
    return 0;
}

练习9.27

#include<iostream>
#include<forward_list>

using namespace std;

int main() {
    forward_list<int> flst = { 0,1,2,3,4,5,6,7,8,9 };
    auto prev = flst.before_begin();
    auto curr = flst.begin();
    while (curr != flst.end()) {
        if (*curr % 2) {
            curr = flst.erase_after(prev);
        }
        else {
            prev = curr;
            ++curr;
        }
    }
    for (auto i : flst) {
        cout << i << " ";
    }
    system("pause");
    return 0;
}

练习9.28

#include<forward_list>
#include<iostream>
#include<string>

using namespace std;

void func(forward_list<string> &flst, string a, string b) {
    auto it = flst.begin();
    auto prev = flst.before_begin();
    bool flag = false;
    while (it != flst.end()) {
        if (*it == a) {
            it = flst.insert_after(it, b);
            flag = true;
            break;
        }
        else {
            prev = it;
            ++it;
        }
    }
    if (!flag) flst.insert_after(prev, b);
}

int main() {
    forward_list<string> flst = { "abc","bcd","eee" };
    string a = "aaa", b = "fff";
    func(flst, a, b);
    for (auto i : flst) {
        cout << i << " ";
    }
    cout << endl;
    system("pause");
    return 0;
}

练习9.29
vec.resize(100)会将90个值为0的元素添加到末尾。
vec.resize(10)会将末尾90个元素删去。

练习9.30
元素类型必须提供一个默认的构造函数。

练习9.31
list

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

int main() {
    list<int> lst = { 0,1,2,3,4,5,6,7,8,9 };
    auto iter = lst.begin();
    while (iter != lst.end()) {
        if (*iter % 2) {
            iter = lst.insert(iter, *iter);
            ++iter;
            ++iter;
        }
        else {
            iter = lst.erase(iter);
        }
    }
    for (auto i : lst) {
        cout << i << " ";
    }
    system("pause");
    return 0;
}

forward_list

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

int main() {
    forward_list<int> lst = { 0,1,2,3,4,5,6,7,8,9 };
    auto iter = lst.begin();
    auto prev = lst.before_begin();
    while (iter != lst.end()) {
        if (*iter % 2) {
            iter = lst.insert_after(iter, *iter);
            prev = iter;
            ++iter;
        }
        else {
            iter = lst.erase_after(prev);
        }
    }
    for (auto i : lst) {
        cout << i << " ";
    }
    system("pause");
    return 0;
}

练习9.34
行为是奇数复制，但由于每次插入奇数后返回的是仍是同一个奇数，于是会进入无限循环，应在每次插入奇数后跳过当前数。

#include<vector>
#include<iostream>

using namespace std;

int main() {
    vector<int> v = { 1,2,3,4,5 };
    auto iter = v.begin();
    while (iter != v.end()) {
        if (*iter % 2) {
            iter = v.insert(iter, *iter);
            ++iter;
        }
        ++iter;
    }
    for (auto i : v) {
        cout << i << " ";
    }
    system("pause");
    return 0;
}

练习9.37
list所占的空间不是连续的，array是固定size

练习9.38

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

using namespace std;

int main()
{
    vector<string> v;

    for (string buffer; cin >> buffer; v.push_back(buffer))
        cout << v.size() << " " << v.capacity() << endl;

    return 0;
}

练习9.39
为svec预留了1024的空间，将输入添加到svec中，最后将svec的size增大当前的一半。

练习9.41

vector<char> v = { 'a','b','c' };
string s(v.begin(), v.end());

练习9.42

string s;
s.reserve(100);

练习9.43

#include<iostream>
#include<string>

using namespace std;

void func(string &s, string &oldVal, string &newVal) {
    auto iter = s.begin();
    while (iter + oldVal.size() != s.end()) {
        if (oldVal == string(iter, iter + oldVal.size())) {
            iter = s.erase(iter, iter + oldVal.size());
            iter = s.insert(iter, newVal.begin(), newVal.end());
            iter += newVal.size();
        }
        else {
            ++iter;
        }
    }
}

int main() {
    string s("though,you don't love me");
    string oldVal("though");
    string newVal("tho");
    func(s, oldVal, newVal);
    cout << s;

    system("pause");
    return 0;
}

练习9.44

#include<iostream>
#include<string>

using namespace std;

void func(string &s, string &oldVal, string &newVal) {
    string::size_type i = 0;
    auto s_len = s.size(), old_len = oldVal.size();
    while (i + old_len <= s_len) {
        if (oldVal == s.substr(i, i + old_len)) {
            s.replace(i, i + old_len, newVal);
            i += newVal.size();
        }
        else {
            ++i;
        }
    }
}
int main() {
    string s("though,you don't love me");
    string oldVal("though");
    string newVal("tho");
    func(s, oldVal, newVal);
    cout << s << endl;

    system("pause");
    return 0;
}

练习9.45

#include<iostream>
#include<string>

using namespace std;

void func(string &name, string &pre, string &post) {
    name.insert(0, pre);
    name.append(post);
}

int main() {
    string nm = "John", pre = "Mr.", post = " Jr.";
    func(nm, pre, post);
    cout << nm;
    system("pause");
    return 0;
}

练习9.46

void func(string &name, string &pre, string &post) {
    name.insert(0, pre);
    name.insert(name.size(), post);
}

练习9.47

#include<string>
#include<iostream>

using namespace std;

int main() {
    string str("ab2c3d7R4E6");
    string numbers{ "123456789" };
    string alphabet{ "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ" };
    string::size_type pos = 0;
    while ((pos = str.find_first_of(numbers, pos)) != string::npos) {
        cout << str[pos] << " ";
        ++pos;
    }
    cout << endl;
    pos = 0;
    while ((pos = str.find_first_of(alphabet, pos)) != string::npos) {
        cout << str[pos] << " ";
        ++pos;
    }
    cout << endl;

    pos = 0;
    while ((pos = str.find_first_not_of(alphabet, pos)) != string::npos) {
        cout << str[pos] << " ";
        ++pos;
    }
    cout << endl;

    pos = 0;
    while ((pos = str.find_first_not_of(numbers, pos)) != string::npos) {
        cout << str[pos] << " ";
        ++pos;
    }
    cout << endl;

    system("pause");
    return 0;
}

练习9.48
string::npos

练习9.49

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

using namespace std;

int main() {
    string FileName;
    cout << "请输入要打开的单词文件：" << endl;
    cin >> FileName;
    ifstream inFile(FileName);
    if (!inFile) {
        cout << "打开失败！" << endl;
        return 0;
    }
    vector<string> ans;
    string up("bdfhklt"), down("gjpqy"), s;
    string::size_type pos = 0,poschar;
    while (inFile >> s) {
        if ((pos = s.find_first_of(up)) == string::npos) {
            if ((pos = s.find_first_of(down)) == string::npos) {
                ans.push_back(s);
            }
        }
    }
    for (auto i : ans) {
        cout << i << endl;
    }
    system("pause");
    return 0;
}

练习9.50

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

int main() {
    vector<string> vec = { "2","3","4","50" };
    int sum = 0;
    for (auto i : vec) {
        sum += stoi(i);
    }
    cout << sum << endl;

    system("pause");
    return 0;
}

练习9.51

#include<iostream>
#include<string>

using namespace std;

const string mm[12] = { "Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sept","Oct","Nov","Dec" };

int findmonth(const string &mon) {
    int pos;
    for (int i = 0;i < 12;++i) {
        if ((pos = mon.find(mm[i])) != string::npos) {
            return i + 1;
        }
    }
}

class Date {
public:
    Date(const string &str) {
        string data_str = str;
        string::size_type index1 = 0;
        string::size_type index2 = 0;
        if (str.find(',') != string::npos) {
            index1 = str.find(' ');
            index2 = str.find(',',index1+1);
            string mon = str.substr(0, index1 - 1);
            month = findmonth(mon);
            day = stoi(str.substr(index1 + 1, index2));
            year = stoi(str.substr(index2 + 1));
        }
        else if (str.find('/') != string::npos) {
            index1 = str.find_first_of('/');
            index2 = str.find_first_of('/', index1 + 1);
            year = stoi(str.substr(index2 + 1));
            month = stoi(str.substr(index1 + 1, index2 - 1));
            day = stoi(str.substr(0, index1));
        }
        else {
            index1 = str.find_first_of(' ');
            index2 = str.find_first_of(' ', index1 + 1);
            string mon = str.substr(0, index1);
            month = findmonth(mon);
            day = stoi(str.substr(index1 + 1, index2 - 1));
            year = stoi(str.substr(index2 + 1));
        }
    }
    void getdate() {
        cout << "Year:" << year << " " << "Month:" << month << " " << "Day:" << day << endl;
    }
private:
    unsigned year, month, day;
};


int main() {
    string d1 = "January 1,1900", d2 = "1/1/1990", d3 = "Jan 1 1900";
    Date a(d1), b(d2), c(d3);
    a.getdate();
    b.getdate();
    c.getdate();

    system("pause");
    return 0;
}

练习9.52
题目意思表述的不太清楚，但大意是利用栈来求带括号表达式的值，下面只考虑加法的情况。
如果考虑加减乘除四则运算代码比较复杂，最好先转换成后缀表达式再求值。

#include<iostream>
#include<stack>
#include<string>
using namespace std;

bool isnum(char a) {
    if (a >= '0'&&a <= '9') {
        return true;
    }
    else return false;
}

int main() {
    string expr("(1+2)+(3+4)+5");
    stack<char> st;
    int sum = 0;
    int len = expr.size();
    for (int i = 0;i < len;i++) {
        if (expr[i] == '('|| isnum((expr[i]))) {
            st.push(expr[i]);
        }
        else if (expr[i] == '+') {
            continue;
        }
        else if (expr[i] == ')') {
            while (st.top() != '(') {
                sum += st.top() - '0';
                st.pop();
            }
            st.pop();
        }
    }
    while (!st.empty()) {
        sum += st.top() - '0';
        st.pop();
    }
    cout << sum << endl;

    system("pause");
    return 0;
}

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