Accelerated C++ Chapter 04
どうもです。
Chapter04です。振り返ると，だんだんとテストが欲しくなってきていた頃だった気が。
Exercise 4-1
型が違うから怒られる。
Exercise 4-2
#include <iostream> #include <cmath> #include <iomanip> using std::cout; using std::endl; using std::setw; int main() { for (int i = 0; i <= 100; ++i) { cout << setw(5) << i << " " << setw(5) << i * i << endl; } return 0; }
Exercise 4-3
#include <iostream> #include <cmath> #include <iomanip> using std::cout; using std::endl; using std::setw; int main() { const int upper = 10000; int w = 1; for (int i = upper - 1; i / 10 != 0; i /= 10) { ++w; } for (int i = 0; i < upper; ++i) { cout << setw(w) << i << " " << setw(w * 2) << i * i << endl; } return 0; }
Exercise 4-4
最初，square を square root と勘違いしてた。
#include <iostream> #include <cmath> #include <iomanip> using std::cout; using std::endl; using std::setw; using std::streamsize; using std::setprecision; using std::setiosflags; using std::ios_base; int main() { const double upper = 100; int intpart_width = 1; for (int i = (upper + 1) - 1; i / 10 > 0; i /= 10) { ++intpart_width; } const streamsize prec = 3; // + 1 for a floating point const int left_width = intpart_width + prec + 1; const int right_width = intpart_width * 2 + 1 + prec; streamsize prec_org = cout.precision(); for (double d = 0; d < upper; d += 0.1) { // We need fixed notaion rather than scientific notation. cout << setiosflags(ios_base::fixed); cout << setw(left_width) << setprecision(prec) << d << " " << setw(right_width) << setprecision(prec) << d * d << endl; cout << setprecision(prec_org); } return 0; }
- 実行結果
長いので一部省略。
% ./ex4-4 0.000 0.000 0.100 0.010 0.200 0.040 0.300 0.090 0.400 0.160 0.500 0.250 0.600 0.360 0.700 0.490 0.800 0.640 0.900 0.810 1.000 1.000 1.100 1.210 1.200 1.440 1.300 1.690 1.400 1.960 1.500 2.250 1.600 2.560 1.700 2.890 1.800 3.240 1.900 3.610 2.000 4.000 2.100 4.410 2.200 4.840 2.300 5.290 2.400 5.760 2.500 6.250 2.600 6.760 2.700 7.290 2.800 7.840 2.900 8.410 3.000 9.000 3.100 9.610 3.200 10.240 3.300 10.890 ## ... omitted 98.100 9623.610 98.200 9643.240 98.300 9662.890 98.400 9682.560 98.500 9702.250 98.600 9721.960 98.700 9741.690 98.800 9761.440 98.900 9781.210 99.000 9801.000 99.100 9820.810 99.200 9840.640 99.300 9860.490 99.400 9880.360 99.500 9900.250 99.600 9920.160 99.700 9940.090 99.800 9960.040 99.900 9980.010 100.000 10000.000
Exercise 4-5
構造体を使ったが，(ん? C++では構造体って言わない? 言うよね。)
テキスト中でも登場しているから使ってもいい武器なはず。
#include <iostream> #include <vector> #include <string> #include <stdexcept> #include <algorithm> using namespace std; istream& read_words(istream& in, vector<string>& words) { string word; while (in >> word) { words.push_back(word); } in.clear(); return in; } struct Word { string word_; int occurrence_; }; void push_word_in_vec(const string& word, vector<Word>& words) { // Search for w in words typedef vector<Word>::size_type wvec_sz; for (wvec_sz i = 0; i != words.size(); ++i) { if (word == words[i].word_) { // If found, increment its occurrence ++words[i].occurrence_; return; } } // Push new Word into words Word w; w.word_ = word; w.occurrence_ = 1; words.push_back(w); } void count_occurrences(const vector<string>& words_vec, vector<Word>& words_counter) { for (vector<string>::size_type i = 0; i != words_vec.size(); ++i) { push_word_in_vec(words_vec[i], words_counter); } } bool cmp(const Word& w1, const Word& w2) { return w1.word_ < w2.word_; } int main() { vector<string> words_vec; vector<Word> words_counter; string word; cout << "Enter as many words as you want: "; read_words(cin, words_vec); // count occurrences of each word in words_vec count_occurrences(words_vec, words_counter); // determine the max length string::size_type maxlen = 0; for (vector<string>::size_type i = 0; i != words_vec.size(); ++i) { maxlen = max(maxlen, words_vec[i].size()); } // Sort alphabetically sort(words_counter.begin(), words_counter.end(), cmp); // Display the result cout << endl << "Reoprt: " << endl; cout << "The number of words: " << words_vec.size() << endl; cout << "The occurrences of each word are as follows: " << endl; for (vector<Word>::size_type i = 0; i != words_counter.size(); ++i) { cout << words_counter[i].word_ << string(maxlen - words_counter[i].word_.size() + 3, ' ') << words_counter[i].occurrence_ << endl; } return 0; }
- 実行結果
出力がたくさんなので，一部省略。
% ./ex4-5 < ./ex4-5.cc Enter as many words as you want: Reoprt: The number of words: 257 The occurrences of each word are as follows: != 4 " 3 "; 1 "Enter 1 "Reoprt: 1 "The 2 #include 5 words_vec.size() 1 words_vec.size(); 2 words_vec; 1 words_vec[i].size()); 1 wvec_sz; 1 you 1 { 12 } 11 }; 1
Exercise 4-6
Student_info::read() だけを修正。
たしかこれだけだったはず。
istream& read(istream& is, Student_info& s)
{
is >> s.name >> s.midterm >> s.final;
read_hw(is, s.homework);
s.final_grade = grade(s);
return is;
}
Exercise 4-7
入力がでかかったり，たくさんだったら，あふれると思う。
#include <iostream> #include <vector> using namespace std; double average(const vector<double>& vec) { if (vec.size() == 0) { return 0.0; } double total = 0; for (vector<double>::size_type i = 0; i < vec.size(); i++) { total += vec[i]; } return total / vec.size(); } int main() { double x; vector<double> dvec; while (cin >> x) { dvec.push_back(x); } double avg = average(dvec); cout << "Average = " << avg << endl; for (vector<double>::size_type i = 0; i != dvec.size(); ++i) { cout << dvec[i] << ", "; } cout << endl; return 0; }
