📘 Week 3：陣列與指標

重點：陣列與指標的關係、指標運算
練習:畫記憶體圖,追蹤指標變化

Day 1：陣列基本操作

#include <stdio.h>

int main() {
  int scores[5] = {80, 85, 90, 75, 88};

  for (int i = 0; i < 5; i++) {
    printf("第 %d 位分數：%d\n", i + 1, scores[i]);
  }
  return 0;
}
#include <stdio.h>

int main() {
  int nums[3];
  nums[0] = 10;
  nums[1] = 20;
  nums[2] = nums[0] + nums[1];

  printf("陣列第三項為 %d\n", nums[2]);
  return 0;
}
#include <stdio.h>

int main() {
  char vowels[5] = {'a', 'e', 'i', 'o', 'u'};

  for (int i = 0; i < 5; i++) {
    printf("母音 %d：%c\n", i, vowels[i]);
  }
  return 0;
}
#include <stdio.h>

int main() {
  int data[4] = {1, 2, 3, 4};
  int sum = 0;

  for (int i = 0; i < 4; i++) {
    sum += data[i];
  }
  printf("總和為 %d\n", sum);
  return 0;
}

Day 2：指標基本操作

#include <stdio.h>

int main() {
  int x = 10;
  int *ptr = &x;

  printf("x 的值為 %d\n", x);
  printf("ptr 指向的值為 %d\n", *ptr);
  return 0;
}
#include <stdio.h>

int main() {
  int a = 5;
  int b = 7;
  int *p1 = &a;
  int *p2 = &b;

  printf("p1 指向的值：%d\n", *p1);
  printf("p2 指向的值：%d\n", *p2);
  return 0;
}
#include <stdio.h>

int main() {
  int value = 42;
  int *ptr = &value;

  *ptr = *ptr + 1;
  printf("更新後的值為 %d\n", value);
  return 0;
}
#include <stdio.h>

int main() {
  int num = 100;
  int *p = #

  printf("變數位址：%p\n", p);
  printf("內容值：%d\n", *p);
  return 0;
}

Day 3：陣列與指標的關係

#include <stdio.h>

int main() {
  int arr[3] = {10, 20, 30};
  int *p = arr;

  printf("第一項：%d\n", *p);
  printf("第二項：%d\n", *(p + 1));
  printf("第三項：%d\n", *(p + 2));
  return 0;
}
#include <stdio.h>

void printArray(int *ptr, int size) {
  for (int i = 0; i < size; i++) {
    printf("第 %d 項：%d\n", i, *(ptr + i));
  }
}

int main() {
  int data[4] = {5, 10, 15, 20};
  printArray(data, 4);
  return 0;
}
#include <stdio.h>

int main() {
  int nums[] = {1, 2, 3, 4, 5};
  int *ptr = nums;

  for (int i = 0; i < 5; i++) {
    printf("位址：%p，值：%d\n", ptr + i, *(ptr + i));
  }
  return 0;
}
#include <stdio.h>

void showFirst(int *arr) {
  printf("第一項是 %d\n", arr[0]);
}

int main() {
  int values[3] = {100, 200, 300};
  showFirst(values);
  return 0;
}

Day 4：指標運算與位址偏移

#include <stdio.h>

int main() {
  int x = 50;
  int *p = &x;

  printf("原始值：%d\n", *p);
  *p += 25;
  printf("更新後：%d\n", *p);
  return 0;
}
#include <stdio.h>

void increment(int *ptr) {
  *ptr = *ptr + 1;
}

int main() {
  int value = 99;
  increment(&value);
  printf("加一後的值：%d\n", value);
  return 0;
}
#include <stdio.h>

int main() {
  int arr[] = {3, 6, 9};
  int *p = arr;

  for (int i = 0; i < 3; i++) {
    *(p + i) *= 2;
    printf("第 %d 項加倍後：%d\n", i, *(p + i));
  }
  return 0;
}
#include <stdio.h>

void reset(int *p) {
  for (int i = 0; i < 4; i++) {
    *(p + i) = 0;
  }
}

int main() {
  int data[4] = {1, 2, 3, 4};
  reset(data);

  for (int i = 0; i < 4; i++) {
    printf("第 %d 項：%d\n", i, data[i]);
  }
  return 0;
}

Day 5：陣列指標作為函數參數

#include <stdio.h>

void printSum(int *arr, int size) {
  int sum = 0;
  for (int i = 0; i < size; i++) {
    sum += arr[i];
  }
  printf("總和為 %d\n", sum);
}

int main() {
  int data[4] = {10, 20, 30, 40};
  printSum(data, 4);
  return 0;
}
#include <stdio.h>

void doubleArray(int *arr, int size) {
  for (int i = 0; i < size; i++) {
    arr[i] *= 2;
  }
}

int main() {
  int nums[3] = {1, 2, 3};
  doubleArray(nums, 3);

  for (int i = 0; i < 3; i++) {
    printf("%d ", nums[i]);
  }
  printf("\n");
  return 0;
}
#include <stdio.h>

void resetArray(int *arr, int size) {
  for (int i = 0; i < size; i++) {
    arr[i] = 0;
  }
}

int main() {
  int values[5] = {5, 10, 15, 20, 25};
  resetArray(values, 5);

  for (int i = 0; i < 5; i++) {
    printf("%d ", values[i]);
  }
  printf("\n");
  return 0;
}
#include <stdio.h>

void showLast(int *arr, int size) {
  printf("最後一項是 %d\n", arr[size - 1]);
}

int main() {
  int data[4] = {11, 22, 33, 44};
  showLast(data, 4);
  return 0;
}

Day 6：字元陣列與字串指標

#include <stdio.h>

int main() {
  char name[] = "會安";
  printf("你好，%s！\n", name);
  return 0;
}
#include <stdio.h>

int main() {
  char word[] = "C語言";
  for (int i = 0; word[i] != '\0'; i++) {
    printf("字元 %d：%c\n", i, word[i]);
  }
  return 0;
}
#include <stdio.h>

void printChars(char *str) {
  while (*str != '\0') {
    printf("%c ", *str);
    str++;
  }
  printf("\n");
}

int main() {
  char text[] = "指標";
  printChars(text);
  return 0;
}
#include <stdio.h>

int main() {
  char *msg = "Hello, C!";
  printf("訊息：%s\n", msg);
  return 0;
}

Day 7：指標進階運算與記憶體追蹤

#include <stdio.h>

void showAddresses(int *arr, int size) {
  for (int i = 0; i < size; i++) {
    printf("第 %d 項位址：%p，值：%d\n", i, arr + i, *(arr + i));
  }
}

int main() {
  int data[3] = {100, 200, 300};
  showAddresses(data, 3);
  return 0;
}
#include <stdio.h>

void reverse(int *arr, int size) {
  for (int i = size - 1; i >= 0; i--) {
    printf("%d ", *(arr + i));
  }
  printf("\n");
}

int main() {
  int nums[4] = {1, 2, 3, 4};
  reverse(nums, 4);
  return 0;
}
#include <stdio.h>

void trace(int *p) {
  printf("初始位址：%p\n", p);
  p++;
  printf("偏移後位址：%p\n", p);
}

int main() {
  int x = 10, y = 20;
  int *ptr = &x;
  trace(ptr);
  return 0;
}
#include <stdio.h>

void modify(int *p) {
  *p = *p + 100;
}

int main() {
  int value = 50;
  printf("原始值：%d\n", value);
  modify(&value);
  printf("修改後：%d\n", value);
  return 0;
}