1、计算并输出1到100之间所有偶数之和；

#include <stdio.h>int main(){int sum = 0;for(int i = 2; i <= 100; i+ = 2) {sum+ = i;}printf("sum = :%d\n", sum);return 0;
}

 2、招数数组中的最大值和最小值；

#include <stdio.h>int main() {int a[] = {2, 1, 4, 6, 5};int size = sizeof(a) / sizeof(a[0]);int max = a[0];int min = a[0];for (int i = 0; i < size; i++) {if (a[i] > max) {max = a[i];}if (a[i] < min) {min = a[i];}}printf("max = :%d\n", max);printf("min = :%d\n", min);return 0;
}

 3、将给定的字符串反转；

#include <stdio.h>
#include <string.h>void reverse(char str[]) {int len = strlen(str);for (int i = 0; i < len / 2; i++) {char temp = str[i];str[i] = str[len - i - 1];str[len - i - 1] = temp;}
}int main() {char str[] = "abcd";reverse(str);printf("reverse:%s\n", str);return 0;
}

4、判定一个给定的字符串是否是回文字符串；

#include <stdio.h>
#include <string.h>int palindrome(char str[]) {int len = strlen(str);for (int i = 0; i < len / 2; i++) {if(str[i] != str[len - i - 1]) {return 0;}}return 1;
}int main() {char str[] = "level";if(palindrome(str)) {printf("%s is palindrome\n", str);} else {printf("%s is not a palindrome\n", str);}return 0;
}

5、计算一个给定数字的阶乘；

#include <stdio.h>int factorial(int n) {if (n == 0 || n == 1) {return 1;}return n * factorial(n - 1);
}int main() {int num = 5;int result = factorial(num);printf("factorialof %d is %d\n", num, result);return 0;
}

6、找出一个对给定数组中的所有重复元素；

#include <stdio.h>void findDuplicates(int a[], int size) {for (int i = 0; i < size; i++) {for(int j = i + 1; j < size; j++) {if (a[i] == a[j]) {printf("%d is aduplicate\n", a[i]);}}}
}int main() {int a[] = {2, 3, 4, 2, 5, 6, 4, 3};int size = sizeof(a) / sizeof(a[0]);findDuplicates(a, size);return 0;
}

7、将一个给定的整数数组按升序排序；

#include <stdio.h>void bubbleSort(int a[], int size) {for (int i = 0; i < size - 1; i++) {for (int j = 0; j < size - i - 1; j++) {if (a[j] > a[j + 1]) {int temp = a[j];a[j] = a[j + 1];a[j + 1] = temp;}}}
}int main() {int a[] = {5, 2, 9, 1, 7};int size = sizeof(a) / sizeof(a[0]);bubbleSort(a, size);printf("Sorted array in ascending order: ");for (int i = 0; i < size; i++) {printf("%d ", a[i]);}printf("\n");return 0;
}

8、判断一个给定的字符串是否是有效的ip地址；

#include <stdio.h>
#include <string.h>int ipAddress(char str[]) {int count = 0;char *token = strtok(str, ".");while (token != NULL) {int num = atoi(token);if (num < 0 || num > 255) {retturn 0;}count++;token = strtok(NULL, ".");}return (count == 4);
}int main() {char str[] = "192.168.0.1";if(ipAddress(str)) {printf("%s 是一个有效IP地址\n", str);} else {printf("%s 不是一个有效的IP地址\n", str);}return 0;
}

 9、判断一个给定的字符串是否是有效的括号序列（左右括号数量是否一致）；

#include <stdio.h>
#include <string.h>int vaild(char str[]) {int len = strlen(str);int count = 0;for (int i = 0; i < len; i++) {if (str[i] == '(')  {count++;} else if (str[i] == ')') {count--;}if (count < 0) {return 0;}}return (count == 0);
}int main() {char str[] = "((()))";if (vaild(str)) {printf("%s 是一个有效的括号\n", str);} else {printf("%s 不是一个有效的括号\n", str);}return 0;
}

10、将一个给定的字符串中的所有空格替换为“%20”；

#include <stdio.h>
#include <string.h>void spaces(char str[]) {int len = strlen(str);int count = 0;for (int i = 0; i < len; i++) {if (str[i] = ' ') {count++;}}int newlen = len + 2 * count;str[newlen] = '\0';for(int i = len - 1; i >= 0; i--) {if (str[i] == ' ' ) {str[newlen - 1] = '0';str[newlen - 2] = '2';sre[newlen - 3] = '%';newlen--;} else {str[newlen - 1] = str[i];newlen--;}}
}int main () {char str[] = "hello world";spaces(str);printf("空格替换后的字符串：%s\n", str);return 0;
}