C示例集
学编程最好的方式就是多写代码。这些小程序各有侧重，挑感兴趣的练一练。
九九乘法表
C
#include <stdio.h>
int main(void) {
for (int i = 1; i <= 9; i++) {
for (int j = 1; j <= i; j++) {
printf("%d*%d=%-4d", j, i, i * j);
}
printf("\n");
}
return 0;
}
TEXT
1*1=1
1*2=2 2*2=4
1*3=3 2*3=6 3*3=9
1*4=4 2*4=8 3*4=12 4*4=16
1*5=5 2*5=10 3*5=15 4*5=20 5*5=25
1*6=6 2*6=12 3*6=18 4*6=24 5*6=30 6*6=36
1*7=7 2*7=14 3*7=21 4*7=28 5*7=35 6*7=42 7*7=49
1*8=8 2*8=16 3*8=24 4*8=32 5*8=40 6*8=48 7*8=56 8*8=64
1*9=9 2*9=18 3*9=27 4*9=36 5*9=45 6*9=54 7*9=63 8*9=72 9*9=81
素数判断
C
#include <stdio.h>
#include <math.h>
int is_prime(int n) {
if (n < 2) return 0;
if (n == 2) return 1;
if (n % 2 == 0) return 0;
for (int i = 3; i <= (int)sqrt(n); i += 2) {
if (n % i == 0) return 0;
}
return 1;
}
int main(void) {
int start = 2, end = 100;
printf("%d到%d之间的素数:\n", start, end);
int count = 0;
for (int i = start; i <= end; i++) {
if (is_prime(i)) {
printf("%4d", i);
count++;
if (count % 10 == 0) printf("\n");
}
}
if (count % 10 != 0) printf("\n");
printf("共%d个素数\n", count);
return 0;
}
TEXT
2到100之间的素数:
2 3 5 7 11 13 17 19 23 29
31 37 41 43 47 53 59 61 67 71
73 79 83 89 97
共25个素数
文件复制
C
#include <stdio.h>
int main(int argc, char *argv[]) {
if (argc != 3) {
fprintf(stderr, "用法: %s 源文件 目标文件\n", argv[0]);
return 1;
}
FILE *src = fopen(argv[1], "rb");
if (src == NULL) {
perror("无法打开源文件");
return 1;
}
FILE *dst = fopen(argv[2], "wb");
if (dst == NULL) {
perror("无法创建目标文件");
fclose(src);
return 1;
}
char buf[4096];
size_t bytes;
while ((bytes = fread(buf, 1, sizeof(buf), src)) > 0) {
fwrite(buf, 1, bytes, dst);
}
fclose(src);
fclose(dst);
printf("复制完成\n");
return 0;
}
字符串反转
C
#include <stdio.h>
#include <string.h>
void str_reverse(char *str) {
int len = strlen(str);
for (int i = 0; i < len / 2; i++) {
char tmp = str[i];
str[i] = str[len - 1 - i];
str[len - 1 - i] = tmp;
}
}
int main(void) {
char str1[] = "Hello, World!";
str_reverse(str1);
printf("%s\n", str1);
char str2[] = "ABCDEF";
str_reverse(str2);
printf("%s\n", str2);
return 0;
}
TEXT
!dlroW ,olleH
FEDCBA
斐波那契数列
C
#include <stdio.h>
long fibonacci(int n) {
if (n <= 0) return 0;
if (n == 1) return 1;
long a = 0, b = 1;
for (int i = 2; i <= n; i++) {
long next = a + b;
a = b;
b = next;
}
return b;
}
int main(void) {
for (int i = 0; i <= 20; i++) {
printf("F(%d) = %ld\n", i, fibonacci(i));
}
return 0;
}
TEXT
F(0) = 0
F(1) = 1
F(2) = 1
F(3) = 2
F(4) = 3
F(5) = 5
...
F(20) = 6765
冒泡排序
C
#include <stdio.h>
void bubble_sort(int arr[], int n) {
for (int i = 0; i < n - 1; i++) {
int swapped = 0;
for (int j = 0; j < n - 1 - i; j++) {
if (arr[j] > arr[j + 1]) {
int tmp = arr[j];
arr[j] = arr[j + 1];
arr[j + 1] = tmp;
swapped = 1;
}
}
if (!swapped) break;
}
}
int main(void) {
int arr[] = {64, 34, 25, 12, 22, 11, 90};
int n = sizeof(arr) / sizeof(arr[0]);
printf("排序前: ");
for (int i = 0; i < n; i++) printf("%d ", arr[i]);
printf("\n");
bubble_sort(arr, n);
printf("排序后: ");
for (int i = 0; i < n; i++) printf("%d ", arr[i]);
printf("\n");
return 0;
}
TEXT
排序前: 64 34 25 12 22 11 90
排序后: 11 12 22 25 34 64 90
猜数字游戏
C
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int main(void) {
srand((unsigned int)time(NULL));
int target = rand() % 100 + 1;
int guess, attempts = 0;
printf("猜一个1到100之间的数字\n");
while (1) {
printf("你的猜测: ");
if (scanf("%d", &guess) != 1) {
printf("请输入有效数字\n");
while (getchar() != '\n');
continue;
}
attempts++;
if (guess < target) {
printf("太小了！\n");
} else if (guess > target) {
printf("太大了！\n");
} else {
printf("恭喜！你用了%d次猜中了！\n", attempts);
break;
}
}
return 0;
}
学生成绩管理
C
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct {
char name[32];
int id;
float scores[3];
float average;
} Student;
void calc_average(Student *s) {
s->average = (s->scores[0] + s->scores[1] + s->scores[2]) / 3.0f;
}
void print_student(const Student *s) {
printf("%-20s %4d %6.1f %6.1f %6.1f %6.1f\n",
s->name, s->id,
s->scores[0], s->scores[1], s->scores[2],
s->average);
}
int cmp_by_average(const void *a, const void *b) {
float diff = ((const Student *)a)->average - ((const Student *)b)->average;
return (diff > 0) ? -1 : ((diff < 0) ? 1 : 0);
}
int main(void) {
Student students[] = {
{"张三", 101, {85, 90, 78}, 0},
{"李四", 102, {92, 88, 95}, 0},
{"王五", 103, {76, 82, 70}, 0},
{"赵六", 104, {98, 95, 92}, 0}
};
int n = sizeof(students) / sizeof(students[0]);
for (int i = 0; i < n; i++) {
calc_average(&students[i]);
}
printf("%-20s %4s %6s %6s %6s %6s\n",
"姓名", "学号", "语文", "数学", "英语", "平均");
printf("------------------------------------------------------\n");
for (int i = 0; i < n; i++) {
print_student(&students[i]);
}
qsort(students, n, sizeof(Student), cmp_by_average);
printf("\n按平均分排序:\n");
printf("%-20s %4s %6s\n", "姓名", "学号", "平均分");
printf("------------------------------------\n");
for (int i = 0; i < n; i++) {
printf("%-20s %4d %6.1f\n",
students[i].name, students[i].id, students[i].average);
}
return 0;
}
TEXT
姓名 学号 语文 数学 英语 平均
------------------------------------------------------
张三 101 85.0 90.0 78.0 84.3
李四 102 92.0 88.0 95.0 91.7
王五 103 76.0 82.0 70.0 76.0
赵六 104 98.0 95.0 92.0 95.0
按平均分排序:
姓名 学号 平均分
------------------------------------
赵六 104 95.0
李四 102 91.7
张三 101 84.3
王五 103 76.0
单词统计
C
#include <stdio.h>
#include <ctype.h>
int main(void) {
int ch;
int chars = 0, words = 0, lines = 0;
int in_word = 0;
while ((ch = getchar()) != EOF) {
chars++;
if (ch == '\n') {
lines++;
}
if (isspace(ch)) {
in_word = 0;
} else {
if (!in_word) {
words++;
in_word = 1;
}
}
}
printf("字符数: %d\n", chars);
printf("单词数: %d\n", words);
printf("行数: %d\n", lines);
return 0;
}
进制转换
C
#include <stdio.h>
#include <string.h>
void to_binary(unsigned int n, char *buf, int size) {
buf[size - 1] = '\0';
for (int i = size - 2; i >= 0; i--) {
buf[i] = (n & 1) + '0';
n >>= 1;
}
}
void to_hex(unsigned int n, char *buf, int size) {
const char digits[] = "0123456789ABCDEF";
buf[size - 1] = '\0';
for (int i = size - 2; i >= 0; i--) {
buf[i] = digits[n & 0xF];
n >>= 4;
}
}
int main(void) {
unsigned int values[] = {42, 255, 1024, 65535};
int count = sizeof(values) / sizeof(values[0]);
printf("%-10s %-34s %-10s\n", "十进制", "二进制", "十六进制");
printf("----------------------------------------------------\n");
for (int i = 0; i < count; i++) {
char bin[33], hex[9];
to_binary(values[i], bin, sizeof(bin));
to_hex(values[i], hex, sizeof(hex));
printf("%-10u %-34s 0x%s\n", values[i], bin, hex);
}
return 0;
}
TEXT
十进制 二进制 十六进制
----------------------------------------------------
42 00000000000000000000000000101010 0x2A
255 00000000000000000000000011111111 0xFF
1024 00000000000000000000010000000000 0x400
65535 00000000000000001111111111111111 0xFFFF
简易计算器
C
#include <stdio.h>
#include <stdlib.h>
int main(void) {
double a, b, result;
char op;
printf("输入表达式（如 3 + 5）: ");
if (scanf("%lf %c %lf", &a, &op, &b) != 3) {
printf("输入格式错误\n");
return 1;
}
switch (op) {
case '+': result = a + b; break;
case '-': result = a - b; break;
case '*': result = a * b; break;
case '/':
if (b == 0) {
printf("错误：除数不能为零\n");
return 1;
}
result = a / b;
break;
case '%':
if ((int)b == 0) {
printf("错误：取余的除数不能为零\n");
return 1;
}
result = (int)a % (int)b;
break;
default:
printf("不支持的操作符: %c\n", op);
return 1;
}
printf("%.2f %c %.2f = %.2f\n", a, op, b, result);
return 0;
}
回文判断
C
#include <stdio.h>
#include <string.h>
#include <ctype.h>
int is_palindrome(const char *str) {
int left = 0;
int right = strlen(str) - 1;
while (left < right) {
while (left < right && !isalnum((unsigned char)str[left])) left++;
while (left < right && !isalnum((unsigned char)str[right])) right--;
if (tolower((unsigned char)str[left]) != tolower((unsigned char)str[right])) {
return 0;
}
left++;
right--;
}
return 1;
}
int main(void) {
const char *tests[] = {
"racecar",
"A man a plan a canal Panama",
"hello",
"12321",
"Was it a car or a cat I saw"
};
int n = sizeof(tests) / sizeof(tests[0]);
for (int i = 0; i < n; i++) {
printf("\"%s\" -> %s\n", tests[i],
is_palindrome(tests[i]) ? "是回文" : "不是回文");
}
return 0;
}
TEXT
"racecar" -> 是回文
"A man a plan a canal Panama" -> 是回文
"hello" -> 不是回文
"12321" -> 是回文
"Was it a car or a cat I saw" -> 是回文
矩阵乘法
C
#include <stdio.h>
void matrix_multiply(int A[2][3], int B[3][2], int C[2][2]) {
for (int i = 0; i < 2; i++) {
for (int j = 0; j < 2; j++) {
C[i][j] = 0;
for (int k = 0; k < 3; k++) {
C[i][j] += A[i][k] * B[k][j];
}
}
}
}
void print_matrix_2x3(int m[2][3]) {
for (int i = 0; i < 2; i++) {
for (int j = 0; j < 3; j++) {
printf("%4d", m[i][j]);
}
printf("\n");
}
}
void print_matrix_3x2(int m[3][2]) {
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 2; j++) {
printf("%4d", m[i][j]);
}
printf("\n");
}
}
void print_matrix_2x2(int m[2][2]) {
for (int i = 0; i < 2; i++) {
for (int j = 0; j < 2; j++) {
printf("%4d", m[i][j]);
}
printf("\n");
}
}
int main(void) {
int A[2][3] = {{1, 2, 3}, {4, 5, 6}};
int B[3][2] = {{7, 8}, {9, 10}, {11, 12}};
int C[2][2];
printf("矩阵A (2x3):\n");
print_matrix_2x3(A);
printf("矩阵B (3x2):\n");
print_matrix_3x2(B);
matrix_multiply(A, B, C);
printf("A x B (2x2):\n");
print_matrix_2x2(C);
return 0;
}
TEXT
矩阵A (2x3):
1 2 3
4 5 6
矩阵B (3x2):
7 8
9 10
11 12
A x B (2x2):
58 64
139 154
二分查找
C
#include <stdio.h>
int binary_search(int arr[], int n, int target) {
int left = 0, right = n - 1;
while (left <= right) {
int mid = left + (right - left) / 2;
if (arr[mid] == target) {
return mid;
} else if (arr[mid] < target) {
left = mid + 1;
} else {
right = mid - 1;
}
}
return -1;
}
int main(void) {
int arr[] = {2, 5, 8, 12, 16, 23, 38, 45, 56, 72, 91};
int n = sizeof(arr) / sizeof(arr[0]);
int targets[] = {23, 7, 72, 1};
int m = sizeof(targets) / sizeof(targets[0]);
for (int i = 0; i < m; i++) {
int idx = binary_search(arr, n, targets[i]);
if (idx >= 0) {
printf("找到 %d，下标 %d\n", targets[i], idx);
} else {
printf("未找到 %d\n", targets[i]);
}
}
return 0;
}
TEXT
找到 23，下标 5
未找到 7
找到 72，下标 9
未找到 1
凯撒加密
C
#include <stdio.h>
void caesar_encrypt(char *text, int shift) {
for (int i = 0; text[i] != '\0'; i++) {
if (text[i] >= 'A' && text[i] <= 'Z') {
text[i] = 'A' + (text[i] - 'A' + shift) % 26;
} else if (text[i] >= 'a' && text[i] <= 'z') {
text[i] = 'a' + (text[i] - 'a' + shift) % 26;
}
}
}
void caesar_decrypt(char *text, int shift) {
caesar_encrypt(text, 26 - shift % 26);
}
int main(void) {
char msg[] = "Hello World!";
int shift = 3;
printf("原文: %s\n", msg);
caesar_encrypt(msg, shift);
printf("加密: %s\n", msg);
caesar_decrypt(msg, shift);
printf("解密: %s\n", msg);
return 0;
}
TEXT
原文: Hello World!
加密: Khoor Zruog!
解密: Hello World!
