# WEEK7
## 第一次小考
### 01 calculate the remainder 計算餘數
> 利用 if - else 依序判斷是否可以整除 0 2 5 10 並輸出結果
> 能整除、不能整除要分成兩種情況輸出
```cpp
#include <stdio.h>
int main() {
int x, y;
// Read two integers from the user
scanf("%d", &x);
scanf("%d", &y);
// Calculate the remainder of x divided by y
int remainder = x % y;
if (remainder == 0) {
// x is divisible by y (remainder is 0)
printf("The remainder of %d / %d is 0.\n", x, y);
// Check if x is even
if (x % 2 == 0) {
printf("%d is even.\n", x);
} else {
printf("%d is not even.\n", x);
}
// Check if x is divisible by 5
if (x % 5 == 0) {
printf("%d is divisible by 5.\n", x);
} else {
printf("%d is not divisible by 5.\n", x);
}
// Check if x is divisible by 10
if (x % 10 == 0) {
printf("%d is divisible by 10.\n", x);
} else {
printf("%d is not divisible by 10.\n", x);
}
} else {
printf("The remainder of %d / %d is %d.", x, y, remainder);
}
return 0;
}
```
### 02 scholarship 獎學金
> 建議用 for 迴圈進行五次輸入
> 每輸入一次就用 switch 進行一次計算及輸出
```cpp
#include<stdio.h>
int main(){
int i;
float score;
float total = 0.0;
for(i = 0; i < 5; i++){
scanf("%f",&score);
switch ((int)score/10)
{
case 10:case 9:
printf("A\n");
total += (score * 11);
break;
case 8:
printf("B\n");
total += (score * 9.85);
break;
case 7:
printf("C\n");
total += (score * 7.75);
break;
case 6:
printf("D\n");
total += (score * 5.15);
break;
case 5:case 4:case 3:case 2:case 1:case 0:
printf("F\n");
total += (score * 1.1);
break;
default:
break;
}
}
printf("Total scholarship : %.2f",total);
return 0;
}
```
### 04 distance between two points 兩點間距離
>善用 math.h 中的函數
```cpp
#include <stdio.h>
#include <math.h>
int main() {
int x1, x2, y1, y2;
float distance;
scanf("%d %d %d %d", &x1, &y1, &x2, &y2);
// 計算距離
distance = sqrt(pow(x2 - x1, 2) + pow(y2 - y1, 2));
printf("%.3f", distance);
return 0;
}
```
==要特別注意函式參數的型態!!==
標頭檔 math.h 宣告許多跟數學計算相關的函數 (function) ，如求平方根、指數、對數、三角函數等，大部分函數都是以 double 型態為預設回傳值 (return type) 及參數 (parameter) 的資料型態 (data type) ，也另提供 float 與 long double 型態對應的函數。
[math.h](http://kaiching.org/pydoing/c/c-std-math.html)
### 08 multiplication table 乘法表
> 用 for 迴圈處理重複的問題
```
#include <stdio.h>
main(void){
int x;
scanf("%d,",&x);
int a = x * 1;
int b = x * 2;
int c = x * 3;
int y = x * 4;
int e = x * 5;
int f = x * 6;
int g = x * 7;
int h = x * 8;
int i = x * 9;
int j = x * 10;
printf("%d * 1 = %d",x,a);
printf("\n%d * 2 = %d",x,b);
printf("\n%d * 3 = %d",x,c);
printf("\n%d * 4 = %d",x,y);
printf("\n%d * 5 = %d",x,e);
printf("\n%d * 6 = %d",x,f);
printf("\n%d * 7 = %d",x,g);
printf("\n%d * 8 = %d",x,h);
printf("\n%d * 9 = %d",x,i);
printf("\n%d * 10 = %d",x,j);
}
```
```cpp
#include <stdio.h>
int main() {
int number, i;
scanf("%d", &number);
for (i = 1; i <= 10; ++i) {
printf("%d * %d = %d", number, i, number * i);
printf("\n");
}
return 0;
}
```
### 14 Caesar Cipher Problem 凱薩加密法
> 除了單純加3、最後3個另外處理的做法
> 可以使用 %26 來使字母循環
> 但需要特別注意要先將 ASCII code 的值減去 'A' 在 ASCII 表中的位置(65)
> 讓字母 shift 到 0-26
```cpp
#include<stdio.h>
int main(){
char c;
scanf("%c", &c);
printf("%c", (c-65+3)%26+65);
return 0;
}
```
### 15 3n+1 Problem 3n+1問題
>看起來很難，但其實只要依照題目敘述依序寫出判斷條件即可
```cpp
#include <stdio.h>
int main() {
int n, cycle=1, i;
scanf("%d", &n);
while(n!=1) {
if(n%2 == 1)
n = 3*n+1;
else
n/=2;
cycle++;
}
printf("%d", cycle);
return 0;
}
```
## week7
### 08、09
```cpp
#include <stdio.h>
int main() {
int n;
while(scanf("%d", &n) != EOF) {
//寫程式在這裡
}
return 0;
}
```
[EOF的用法](https://blog.csdn.net/diviner_s/article/details/109502597)
### 作答方式
在下面的 code 區塊將有已經寫好的 code template，大家只需要完成**函數的部分**就可以完成作答。
在自己的編譯器上面測試函數能夠正常使用後，把函數放到底下的提交區塊後提交即可。
### Function
### 怎麼將程式用函式改寫
**原本的程式**
```
#include <stdio.h>
#include <stdlib.h>
int main() {
int n, m;
scanf("%d", &n);
for(int i=0;i<n;i++){
printf("*");
}
printf("\n");
for(int j=0;j<(n-2);j++){
printf("*");
for(int i=0;i<(n-2);i++){
printf(" ");
}
printf("*\n");
}
for(int i=0;i<n;i++){
printf("*");
}
printf("\n");
return 0;
}
```
**改成函式寫法**
```
#include <stdio.h>
#include <stdlib.h>
void print(int);
void print(int n) {
}
int main() {
int n, m;
scanf("%d %d", &n, &m);
print_rectangle(n);
return 0;
}
```
### 11
**Code Template**
```cpp
//PREPEND BEGIN
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
void print();
//PREPEND END
//TEMPLATE BEGIN
#include<stdio.h>
void print() {
// 請完成 function 使其能夠在執行後輸出 Hello World!
// Please complete the function so that when executed, it will output Hello World!
}
//TEMPLATE END
//APPEND BEGIN
int main() {
print();
return 0;
}
//APPEND END
```
**Your Code**
```cpp
#include<stdio.h>
void print() {
printf("Hello World!");
}
```
### 12
```cpp
//PREPEND BEGIN
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
void print_rectangle(int);
void print_trangle(int);
//PREPEND END
//TEMPLATE BEGIN
#include<stdio.h>
void print_rectangle(int n) {
}
void print_trangle(int m) {
}
//TEMPLATE END
//APPEND BEGIN
int main() {
int n, m;
scanf("%d %d", &n, &m);
print_rectangle(n);
print_trangle(m);
return 0;
}
//APPEND END
```
### 13
```cpp
//PREPEND BEGIN
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int diameter(int);
int circumference(int);
int area(int);
//PREPEND END
//TEMPLATE BEGIN
#include<stdio.h>
int diameter(int r){
}
int circumference(int r) {
int pi = 3;
}
int area(int r) {
int pi = 3;
}
//TEMPLATE END
//APPEND BEGIN
int main() {
int r;
scanf("%d", &r);
printf("%d\n%d\n%d", diameter(r), area(r), circumference(r));
return 0;
}
//APPEND END
```
### 14
```cpp
//PREPEND BEGIN
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
char convert(int, int);
//PREPEND END
//TEMPLATE BEGIN
#include<stdio.h>
char convert(int n, int c) {
}
//TEMPLATE END
//APPEND BEGIN
int main() {
int n, c;
scanf("%d %d", &n, &c);
printf("%c", convert(n, c));
return 0;
}
//APPEND END
```
### 15
```cpp
//PREPEND BEGIN
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
void algorithm(int);
//PREPEND END
//TEMPLATE BEGIN
#include<stdio.h>
void algorithm(int n) {
}
//TEMPLATE END
//APPEND BEGIN
int main() {
int n;
scanf("%d", &n);
algorithm(n);
return 0;
}
//APPEND END
```
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