c++ primer练习题答案

第九章课后习题部分答案

《顺序容器》

练习9.5

#include 
using namespace std;

typedef vector<int>::const_iterator it;

bool find(it first, it last, const int val) {
    while (first != last && *first != val) {
        ++first;
    }
    return first != last; // 找到了，则first != last， 若相等，代表没找到
}

int main() {
    vector<int> v = {1, 2, 3, 4, 5, 7};
    cout << find(v.cbegin(), v.cend(), 5) << endl;
    cout << find(v.cbegin(), v.cend(), 6) << endl;
    return 0;
}

练习9.6

#include 
using namespace std;

typedef vector<int>::const_iterator it;

it find(it first, it last, const int val) {
    while (first != last && *first != val) {
        ++first;
    }
    return first; // 找到了，则first != last， 若相等，代表没找到
}

int main() {
    vector<int> v = {1, 2, 3, 4, 5, 7};
    cout << (find(v.cbegin(), v.cend(), 6) == v.cend()) << endl;
    cout << (find(v.cbegin(), v.cend(), 5) == v.cend()) << endl;
    return 0;
}

练习9.7

int main() {
    list<int> l1;
    list<int>::iterator it1 = l1.begin(), it2 = l1.end();
    while (it1 != it2) {
        
    }
    return 0;
}

练习9.10

int main() {
    vector<int> v1;
    const vector<int> v2;
    vector<int>::iterator it1 = v1.begin();
    vector<int>::const_iterator it2 = v2.begin();
    vector<int>::const_iterator it3 = v1.cbegin();
    vector<int>::const_iterator it4 = v2.cbegin();
    return 0;
}

练习9.11

#include 
using  namespace std;

typedef vector<int> C;

void print(C& c) {
    for (int v : c) {
        cout << v << ' ';
    }
    cout << endl;
}

int main() {

    // 1
    C c1; // {}

    C c = {1, 2, 3};
    // 2
    C c2(c); // {1, 2, 3}
    // 3
    C c3 = c; // {1, 2, 3}

    // 4
    C c4{1, 2, 3}; // {1, 2, 3}
    // 5
    C c5 = {1, 2, 3}; // {1, 2, 3}
    // 6
    C c6(c.begin(), c.begin()); // {1, 2, 3}

    // test
    print(c);
    print(c1);
    print(c2);
    print(c3);
    print(c4);
    print(c5);
    print(c6);
    return 0;
}

练习9.13

#include 
#include 
using  namespace std;

template <typename T>
void print(T& v) {
    for (auto& c : v) {
        cout << c << ' ';
    }
    cout << endl;
}
int main() {
    list<int> l = {1, 2, 3};
    vector<double> vd(l.begin(), l.end());
    vector<int> vt = {4, 5, 6};
    vector<double> vd2(vt.begin(), vt.end());

    print(l);
    print(vd);
    print(vt);
    print(vd2);

    return 0;
}

练习9.14

#include 
#include 
#include 
using  namespace std;
template <typename T>
void print(T& v) {
    for (auto& c : v) {
        cout << c << ' ';
    }
    cout << endl;
}
int main() {
    list<char*> l = {"aaa", "bbb"};
    vector<string> v(l.begin(), l.end());

    print(l);
    print(v);

    vector<string> v2;
    v2.assign(l.begin(), l.end());
    
    print(v2);
    return 0;
}

练习9.31

#include 
#include 
#include 
using  namespace std;
template <typename T>
void print(T& v) {
    for (auto& c : v) {
        cout << c << ' ';
    }
    cout << endl;
}
int main() {
    list<int> l = {0, 1, 2, 3, 4};
    auto it = l.begin();

    print(l);

    while (it != l.end()) {
        if (*it & 1) {
            it = l.insert(it, *it);
            it++, it++;
        } else {
            it = l.erase(it);
        }
    }

    print(l);
    return 0;
}

练习9.38

int main() {
    vector<int> v;
    int n = 0;
    while (cin >> n) {
        v.clear();
        for (int i = 1;  i <= n; ++ i) {
            v.push_back(i);
            printf("size = %d cap = %d\n", v.size(), v.capacity());
        }
    }
    return 0;
}