C++ Primer Plus 第 6 版 第 3 章 處理數據 — 習題與編程練習參考

複習題精選

• 整型分類原因：單一整型無法滿足所有編程需求。
• `33L` 是 long，`33` 是 int。
• 浮點轉整型可能有捨入誤差，視精度位數而定。
• 字符與整數輸出轉換示例。

編程練習參考答案

3.1 身高換算（英寸 → 英尺+英寸）

int main() {
    int inch; cin >> inch;
    cout << "你身高 " << inch/12 << " 英尺 " << inch%12 << " 英寸\n";
}

3.2 BMI 計算器

const int inch_per_foot = 12;
const double meter_per_inch = 0.0254, pound_per_kg = 2.2;
int foot, inch, pound; cin >> foot >> inch >> pound;
inch = foot*12 + inch;
double meter = inch * meter_per_inch;
double kg = pound / pound_per_kg;
double BMI = kg / meter / meter;
cout << "身高 " << meter << " 米\n體重 " << kg << " 公斤\nBMI " << BMI << endl;

3.3 經緯度轉十進制度

const int min_per_deg = 60, sec_per_min = 60;
int deg, min, sec; cin >> deg >> min >> sec;
double decimal = deg + (double)min/min_per_deg + (double)sec/min_per_deg/sec_per_min;
cout << deg << " degrees, " << min << " minutes, " << sec << " seconds = " << decimal << " degrees";

3.4 秒數轉日時分秒

const int spd = 24*60*60, sph = 60*60, spm = 60;
long sec; cin >> sec;
cout << sec << " seconds = " << sec/spd << " days, "
     << sec%spd/sph << " hours, "
     << sec%spd%sph/spm << " minutes, "
     << sec%spd%sph%spm << " seconds\n";

3.5 人口比例

long long world, US; cin >> world >> US;
cout << "US 人口佔世界 " << (double)US/world*100 << "%\n";

3.6/3.7 英制/公制油耗換算

const double mpk = 0.6214, lpg = 3.785;
// 英裡/加侖 → 升/百公里
double mile, gallon; cin >> mile >> gallon;
double km = mile/mpk, liter = gallon*lpg;
cout << "每百公里 " << liter/km*100 << " 升\n";
// 反向換算同理

本章重點掌握基本類型、常量、輸入輸出及簡單單位換算邏輯。