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Primer C++ 学习笔记(第十章)

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本书为Primer C++ 中文第五版

练习题笔记

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(10.1)
void test1() {
    vector<int> ive = {0, 1, 2, 3, 4, 4, 4, 5};
    int val;
    while(cin >> val && val != 99) {
        cout << count(ive.begin(), ive.end(), val) << endl;
    }
}
(10.2)
void test2() {
    list<string> ive = {"a", "aa", "aaa", "a", "aa", "a", "b", "c"};
    string val;
    while(cin >> val && val != "q") {
        cout << count(ive.begin(), ive.end(), val) << endl;
    }
}

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(10.3)
void test3() {
    vector<double> ive = {0, 1, 2, 3, 4, 4, 4, 5.8};
    cout << accumulate(ive.begin(), ive.end(), 0) << endl;
}
(10.4)
用0的话，则表明结果将会删除小数位。
所以最好是要设置小数位
(10.5)
equal是利用是使用==比较两个元素。
string重载了==，可以比较两个字符串是否等长且其中对应元素相等。
而C风格字符串
1如果是char*类型，没有影响。
2如果是char []类型，用==比较两个对象，会检查两个指针值是否相等，也就是地址是否相等。

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(10.6)
void test6() {
    vector<int> ive(10);
    fill_n(ive.begin(), ive.size(), 0);
    for(auto i : ive) {
        cout << i << " ";
    }
    cout << endl;
}
(10.7)
a:
 //使用copy等算法的时候，确保目的容器至少包含于输入序列一样多的元素。
void test7() {
    list<int> lst; int i;
    while(cin >> i && i != 0)
        lst.push_back(i);
    vector<int> vec(lst.size());
    copy(lst.cbegin(), lst.cend(), vec.begin());
    for(auto i : vec) {
        cout << i << " ";
    }
    cout << endl;
}
或者
void test7() {
    list<int> lst; int i;
    while(cin >> i && i != 0)
        lst.push_back(i);
    vector<int> vec;
    copy(lst.cbegin(), lst.cend(), back_inserter(vec));
    for(auto i : vec) {
        cout << i << " ";
    }
    cout << endl;
}

b:
void test7_2() {
    vector<int> vec;
    //reserve预留空间，没有创建元素对象
    //resize改变容器大小，并且创建对象
    vec.resize(10);
    fill_n(vec.begin(), 10, 0);
    for(auto i : vec) {
        cout << i << " ";
    }
    cout << endl;
}
或者使用back_inserter(vec)；

(10.8)
标准库算法不直接操作容器，而是通过操作迭代器间接访问容器。是否能插入删除元素，取决于传递给这些算法的迭代器是否具有这样的能力。

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(10.9)
void test9() {
    vector<string> sve = {"the", "quick", "red", "fox", "jumps", "over", "the", "slow", "red", "turtle"};
    sort(sve.begin(), sve.end());
    auto end_unique = unique(sve.begin(), sve.end());
    sve.erase(end_unique, sve.end());
    for(auto i : sve) {
        cout << i << " ";
    }
    cout << endl;
}
(10.10)
做到算法和数据结构的分离。
算法不操作具体的容器，只操作迭代器，然后由迭代器实现对容器的访问。
这样做的目的就是实现算法的通用性。

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(10.11)
bool isShorter(const string &s1, const string &s2) {
    return s1.size() < s2.size();
}

void test11() {
    vector<string> sve = {"the", "quick", "red", "fox", "jumps", "over", "the", "slow", "red", "turtle"};
    sort(sve.begin(), sve.end());
    auto end_unique = unique(sve.begin(), sve.end());
    sve.erase(end_unique, sve.end());
    for(auto i : sve) {
        cout << i << " ";
    }
    cout << endl;
    sort(sve.begin(), sve.end(), isShorter);
    for(auto i : sve) {
        cout << i << " ";
    }
    cout << endl;
}

(10.12)
struct Sales_data {
    string bookNo;
    Sales_data(string bn) {
        bookNo = bn;
    };
    string isbn() {
        return bookNo;
    };
};

bool compareIsbn(Sales_data &sd1, Sales_data &sd2) {
    return sd1.isbn().size() < sd2.isbn().size();
}

void test12() {
    Sales_data book1("zl");
    Sales_data book2("zzzl");
    Sales_data book3("zzl");
    Sales_data book4("lz");
    vector<Sales_data> vsd = {book1, book2, book3, book4};
    sort(vsd.begin(), vsd.end(), compareIsbn);
    for(auto i : vsd) {
        cout << i.bookNo << " ";
    }
    cout << endl;
}

(10.13)
bool sizeMore5(const string &s) {
    return s.size() >= 5;
}

void test13() {
    vector<string> sve = {"the", "quick", "red", "fox", "jumps", "over", "the", "slow", "red", "turtle"};
    auto it_end = partition(sve.begin(), sve.end(), sizeMore5);
    for(auto cb = sve.cbegin(); cb < it_end; cb++) {
        cout << *cb << " ";
    }
    cout << endl;
}

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(10.14)
void test14() {
    auto sum = [](int a, int b){return a+b;};
    cout << sum(3, 4) << endl;
}
(10.15)
void test15() {
    int m =10;
    auto sum = [m](int a){return a+m;};
    cout << sum(5) << endl;
}
(10.16)
void biggies(vector<string> &words, vector<string>::size_type sz) {
    sort(words.begin(), words.end());
    auto end_unique = unique(words.begin(), words.end());
    words.erase(end_unique, words.end());
    stable_sort(words.begin(), words.end(),
                [](const string &s1, const string &s2){return s1.size() < s2.size();});
    auto wc = find_if(words.begin(), words.end(),
                [sz](string &s){return s.size() >= sz;});
    auto count = words.end() - wc;
    cout << count << " "<< (count > 1 ? "words" : "word") << " of length "
         << sz << " or longger" << endl;
    for_each(wc, words.end(), [](string &s){ cout << s << " ";});
    cout << endl;

}

void test16() {
    vector<string> sve = {"the", "quick", "red", "fox", "jumps", "over", "the", "slow", "red", "turtle"};
    biggies(sve, 5);
}
(10.17)
void test17() {
    Sales_data book1("zl");
    Sales_data book2("zzzl");
    Sales_data book3("zzl");
    Sales_data book4("lz");
    vector<Sales_data> vsd = {book1, book2, book3, book4};
    sort(vsd.begin(), vsd.end(),
        [](Sales_data &sd1, Sales_data &sd2){return sd1.isbn().size() < sd2.isbn().size();});
    for(auto i : vsd) {
        cout << i.bookNo << " ";
    }
    cout << endl;
}
(10.18)
void test18(){
    vector<string> words = {"the", "quick", "red", "fox", "jumps", "over", "the", "slow", "red", "turtle"};
    int sz = 5;
    sort(words.begin(), words.end());
    auto end_unique = unique(words.begin(), words.end());
    words.erase(end_unique, words.end());
    stable_sort(words.begin(), words.end(),
                [](const string &s1, const string &s2){return s1.size() < s2.size();});
    auto wc = partition(words.begin(), words.end(),
                [sz](string &s){return s.size() < sz;});
    auto count = words.end() - wc;
    cout << count << " "<< (count > 1 ? "words" : "word") << " of length "
         << sz << " or longger" << endl;
    for_each(wc, words.end(), [](string &s){ cout << s << " ";});
    cout << endl;
}

(10.19)
void test19(){
    vector<string> words = {"the", "quick", "red", "fox", "jumps", "over", "the", "slow", "red", "turtle"};
    int sz = 5;
    sort(words.begin(), words.end());
    auto end_unique = unique(words.begin(), words.end());
    words.erase(end_unique, words.end());
    stable_sort(words.begin(), words.end(),
                [](const string &s1, const string &s2){return s1.size() < s2.size();});
    auto wc = stable_partition(words.begin(), words.end(),
                [sz](string &s){return s.size() < sz;});
    auto count = words.end() - wc;
    cout << count << " "<< (count > 1 ? "words" : "word") << " of length "
         << sz << " or longger" << endl;
    for_each(wc, words.end(), [](string &s){ cout << s << " ";});
    cout << endl;
}

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(10.20)
void test20() {
    vector<string> words = {"the", "quick", "red", "fox", "jumps", "over", "the", "slow", "red", "turtle"};
    auto count = count_if(words.begin(), words.end(),
                [](const string &s){return s.size() > 6;});
    cout << count << endl;
}

(10.21)
void test21() {
    int m = 5;
    auto b = [&m]()->bool{return --m;};
    while(b());
    cout << m << endl;
}

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(10.22)
bool shorterThan(const string &s, int l) {
    return s.size() <= l;
}

void test22() {
    vector<string> words = {"the", "quick", "red", "fox", "jumps", "over", "the", "slow", "red", "turtle"};
    auto count = count_if(words.begin(), words.end(),
                bind(shorterThan, placeholders::_1, 6));
    cout << count << endl;
}

(10.23)
bind接受的参数与它绑定的函数相关，函数接受n个参数，则bind接受n+1个参数
(10.24)
bool shorter(const string &s, int l) {
    return s.size() < l;
}

void test24() {
    vector<int> ive = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
    string s;
    while(cin >> s && s != "q") {
        auto iter = find_if(ive.begin(), ive.end(), bind(shorter, s, placeholders::_1));
        if(iter != ive.end()) cout << *iter << endl;
    }
}

(10.25)
bool check_size(const string &s, int l) {
    return s.size() >= l;
}

void test25() {
    vector<string> words = {"the", "quick", "red", "fox", "jumps", "over", "the", "slow", "red", "turtle"};
    sort(words.begin(), words.end());
    auto end_unique = unique(words.begin(), words.end());
    words.erase(end_unique, words.end());
    stable_sort(words.begin(), words.end(),
                [](const string &s1, const string &s2){return s1.size() < s2.size();});
    auto wc = find_if(words.begin(), words.end(), bind(check_size, placeholders::_1, 5));
    auto count = words.end() - wc;
    cout << count << " "<< (count > 1 ? "words" : "word") << " of length 5 or longger" << endl;
    for_each(wc, words.end(), [](string &s){ cout << s << " ";});
    cout << endl;

}

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(10.26)
back_inserter 创建一个使用push_back的迭代器
front_inserter 穿件一个使用push_front的迭代器
inserter 创建一个使用insert的迭代器，此函数接受第二个参数，这个参数必须是一个指向给定容器的迭代器。元素将被插入到给定迭代器所表示的元素之前。
在使用back_inserter和front_inserter的时候要确保容器支持push_back和push_front。
(10.27)
void test27() {
    vector<int> ive = {1, 2, 2, 3, 3, 3, 4, 5};
    list<int> lst;
    unique_copy(ive.begin(), ive.end(), inserter(lst, lst.begin()));
    for(auto i : lst) cout << i << " ";
    cout << endl;
}

(10.28)
void test28() {
    vector<int> ori = {1, 2, 3, 4, 5, 6, 7, 8, 9};
    vector<int> ive, bve;
    list<int> fve;
    copy(ori.rbegin(), ori.rend(), front_inserter(fve));
    copy(ori.begin(), ori.end(), back_inserter(bve));
    copy(ori.begin(), ori.end(), inserter(ive, ive.begin()));
    for(auto i : fve) cout << i << " ";
    cout << endl;
    for(auto i : bve) cout << i << " ";
    cout << endl;
    for(auto i : ive) cout << i << " ";
    cout << endl;

}

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(10.29)
void test29() {
    ifstream in("test.txt");
    istream_iterator<string> str_it(in), end;
    ostream_iterator<string> out_iter(cout, " ");
    copy(str_it, end, out_iter);
    cout << endl;
}

(10.30)
void test30() {
    istream_iterator<int> in(cin), eof;
    ostream_iterator<int> out(cout, " ");
    vector<int> ive(in, eof);
    sort(ive.begin(), ive.end());
    copy(ive.begin(), ive.end(), out);
}

(10.31)
void test31() {
    istream_iterator<int> in(cin), eof;
    ostream_iterator<int> out(cout, " ");
    vector<int> ive(in, eof);
    sort(ive.begin(), ive.end());
    unique_copy(ive.begin(), ive.end(), out);
}

(10.32)
struct Sale_data {
    string bookNo;
    double price;
    int num;
};

istream &operator>>(istream &is, Sale_data &item) {
    is >> item.bookNo >> item.price >> item.num;
    return is;
}

ostream &operator<<(ostream &os,const Sale_data &item) {
    os << item.bookNo << " " << item.price << " " << item.num;
    return os;
}

bool compareIsbn(const Sale_data &sd1, const Sale_data &sd2) {
    return sd1.bookNo.size() < sd2.bookNo.size();
}

void test32() {
    istream_iterator<Sale_data> in(cin), eof;
    ostream_iterator<Sale_data> out(cout, "\n");
    vector<Sale_data> sve(in, eof);
    copy(sve.begin(), sve.end(), out);
    sort(sve.begin(), sve.end(), compareIsbn);
    copy(sve.begin(), sve.end(), out);
}

(10.33)
void oddEven(const string &in, const string &odd, const string &even) {
    ifstream fin(in);
    ofstream foutodd(odd);
    ofstream fouteven(even);
    istream_iterator<int> i(fin), eof;
    ostream_iterator<int> oodd(foutodd, "\n");
    ostream_iterator<int> oeven(fouteven, "\n");
    while(i != eof) {
        if(*i%2) oodd = *i;
        else oeven = *i;
        i++;
    }
}

void test33() {
    oddEven("num.txt", "odd.txt", "even.txt");
}

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(10.34)
void test34() {
    ifstream fin("num.txt");
    istream_iterator<int> in(fin), eof;
    vector<int> ive(in, eof);
    for(auto rbe = ive.crbegin(); rbe < ive.crend(); ++rbe) {
        cout << *rbe << " ";
    }
    cout << endl;
}

(10.35)
void test35() {
    ifstream fin("num.txt");
    istream_iterator<int> in(fin), eof;
    vector<int> ive(in, eof);
    for(auto end = ive.cend() - 1; end >= ive.cbegin(); --end) {
        cout << *end << " ";
    }
    cout << endl;
}

(10.36)
void test36() {
    list<int> lst = {0, 1, 2, 3, 0, 1, 2, 0, 2, 3, 0, 4};
    auto last = find(lst.crbegin(), lst.crend(), 0);
    cout << *last << *last.base() << endl;
}

(10.37)
void test37() {
    vector<int> ive = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
    list<int> lst(ive.crbegin()+2, ive.crend()-3);
    for(auto i : lst) cout << i << " ";
    cout << endl;
}

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(10.38)
输入迭代器，find和accumulate要求输入迭代器，istream_iterator是一种输入迭代器
输出迭代器，copy函数的第三个参数就是输出迭代器，ostream_iterator类型也是输出迭代器
前向迭代器，replace要求前向迭代器，forward_list上的迭代器是前向迭代器
双向迭代器，reverse要求双向迭代器，处理forward_list，其他标准库都提供符合双向迭代器要求的迭代器
随机访问迭代器，sort要求随机访问迭代器，array、deque、string和vector的迭代器都是随机访问迭代器，用于访问内置数组元素的指针也是。
(10.39)
list上的迭代器属于双向迭代器
vector上的迭代器属于随机访问迭代器
(10.40)
copy要求输出迭代器
reverse要求双向迭代器
unique要求前向迭代器

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(10.41)
replace 把迭代器范围内的old_val替换成new_val
replace_if 把迭代器范围内使得pred为true的值替换成new_val
replace_copy 和 replace() 做的事是一样的，但它的结果会被保存到另一个序列中，而不会改变原始序列
replace_copy_if()，它和 replace_if() 算法是相同的，但它的结果会被保存到另一个序列中

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void test42() {
    list<string> lst = {"the", "quick", "red", "fox", "jumps", "over", "the", "slow", "red", "turtle"};
    lst.sort();
    lst.unique();
    for(auto s : lst) cout << s << " "; cout << endl;
}

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