c语言经典案例题

1. 交换两个数的值：

#include <stdio.h>
#define CRT_SECURE_NO_WARNINGS
int main() {
	int a = 5, b = 10, c = 0;
	c = a;
	a = b;
	b = c;
	printf("a=%d b=%d", a, b);
}

2. 键盘录入一个数组判断数组最大值：

#include <stdio.h>
#define CRT_SECURE_NO_WARNINGS
int main() {
	int max = 0;
	int arr[10] = { 0 };
	for (int i = 0; i < 10; i++) {
		printf("请输入第%d个数：",i+1); //从0开始所以为i+1
		scanf("%d", &arr[i]);       
		if (arr[i] > max) {
			max = arr[i];
		}
	}
	printf("最大值为%d", max);
}

3. 判断闰年：

#include <stdio.h>
#define CRT_SECURE_NO_WARNINGS
int main() {
	int year;
	printf("请输入一个年份：");
	scanf("%d", &year);
	if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {//判断闰年条件
		printf("yes");
	}
	else {
		printf("no");
	}
}

4. 判断大小写字母数组，特殊符号：

#include <stdio.h>
#define CRT_SECURE_NO_WARNINGS
int main() {
	char num;
	printf("输入一个字符数字或特殊符号：");
	scanf("%c", &num);
	if (num >= 'a' && num <= 'z') {
		printf("是小写字母。");
	}
	else if (num >= 'A' && num <= 'Z') {
		printf("是大写字母。");
	}
	else if (num >= '0' && num <='9') {
		printf("是数字。");
	}
	else {
		printf("是特殊符号。");
	}
}

5.输入小写字母转大写字母，输入大写字母转小写字母：

#include <stdio.h>
#define CRT_SECURE_NO_WARNINGS
int main() {
	char ch;
	printf("请输入你要转换的字母：");
	scanf("%c", &ch);
	if (ch >= 'a' && ch <= 'z') {
		ch = ch - 32;
	}
	else if(ch >= 'A' && ch <= 'Z'){
		ch = ch + 32;
		
	}
	else {
		printf("输入不合法.");
	}
	printf("%c", ch);
}

6. 打印三角形：

#include <stdio.h>
#define CRT_SECURE_NO_WARNINGS
int main() {
	for (int i = 0; i <= 6; i++) {
		for (int j = i; j <= 5; j++) {
			printf("*");
		}
		printf("\n");
	}
}

  

7. 打印正三角：

#include <stdio.h>
#define CRT_SECURE_NO_WARNINGS
int main() {
	for (int i = 0; i <= 6; i++) {
		for (int j = 0; j <= i; j++) {
			printf("*");
		}
		printf("\n");
	}
}

  

8. 打印九九乘法表：

#include <stdio.h>
#define CRT_SECURE_NO_WARNINGS
int main() {
	for (int i = 1; i <= 6; i++) {
		for (int j = 1; j <= i; j++) {
			printf("%d*%d=%2d ",j,i,j*i);
		}
		printf("\n");
	}
}

9. 冒泡排序法：

#include <stdio.h>
#define CRT_SECURE_NO_WARNINGS
int main() {
	int arr[10];
	int t = 0;
	for (int i = 0; i < 10; i++) {
		printf("请输入第%d个数：", i + 1);
		scanf("%d", &arr[i]);
	}
	for (int i = 0; i < 10; i++) {
		/*printf("请输入第%d个数：", i + 1);
		scanf("%d", &arr[i]);*/
		for (int j = 0; j < 10 - 1 - i; j++) {    
			if (arr[j + 1] > arr[j]) {    //从大到小，arr[j]>arr[j+1]为从小到大
				t = arr[j];
				arr[j] = arr[j + 1];
				arr[1+ j] = t;
			}
		}
	}
	for (int i = 0; i < 10; i++) {
		printf("%d\t",arr[i]);
	}
	
}

10.累加函数：

#include <stdio.h>
#define CRT_SECURE_NO_WARNINGS
double sum(int kai, int jie) {
	int sum = 0;
	for (int i = kai; i <= jie; i++) {
		sum = sum + i;
	}
	return sum;
}
int main() {
	double num = sum(1, 100);
	printf("和为%5.2f", num);
}

11. 函数输入三个数，输出最大值：

#include <stdio.h>
#define CRT_SECURE_NO_WARNINGS
double max(int a, int b, int c) {
	int arr[3] = { a,b,c };
	int max = 0;
	for (int i = 0; i < 3; i++) {
		if (arr[i] > max){
			max = arr[i];
		}
	}
	return max;
	
}
int main() {
	double number = max(1, 100,2);
	printf("最大值为%4.2f", number);

12.函数给出两个数和符号，给出计算结果：

#include <stdio.h>
#define CRT_SECURE_NO_WARNINGS
int math(int a, int b, char c) {
	int num;
	if (c == '+') {
		num = a + b;
	}
	else if (c == '-') {
		num = a - b;
	}
	else if (c == '*') {
		num = a * b;
	}
	else if (c == '/') {
		num = a / b;
	}
	else if (c == '%') {
		num = a % b;
	}
	else {
		num = printf("输入不合法");

	}
}
int main() {
	int number = math(23,2,'/');
	printf("计算结果为%d", number);
}

 13. 函数求一个数组的和：

#include <stdio.h>
#define CRT_SECURE_NO_WARNINGS
int add(int a[],int length) {
	int sum=0;
	for (int i = 0; i < length; i++) {
		sum = sum + a[i];
	}
	return sum;
}
int main() {
	int a[9] = { 23,34,12,45,12,345,45,67,23 };
	int sum = add(a, 9);
	printf("数组和为%d", sum);
}