#include <stdio.h>
// 文件复制
int main() {int c;while ((c = getchar()) != EOF) {putchar(c);}return 0;
}

/** 编写一个将输入复制到输出的程序,* 并将其中连续的多个空格用一个空格代替.*/
#include <stdio.h>int main() {int c;int flag = 0;   // 当前字符是否为空格while ((c = getchar()) != EOF) {if ((c == ' ' && flag == 0) || (c != ' ')) {putchar(c);flag = !flag;}   }   return 0;
}

#include <stdio.h>#define IN  1   // 单词内
#define OUT 0   // 单词外// 统计行数, 单词数和字符数
int main() {int c;int numLines = 0;       // 行数int numWords = 0;       // 单词数int numCharacters = 0;  // 字符数int state = OUT;while ((c = getchar()) != EOF) {++numCharacters;if (c == '\n') {++numLines;}if (c == ' ' || c == '\t' || c == '\n') {state = OUT;} else if (state == OUT) {state = IN;++numWords;}}printf("%d\t%d\t%d\n", numLines, numWords, numCharacters);return 0;
}

#include <stdio.h>
#define MAXLINE 1000
/** 读入一行字符*/
int getline_s(char *s, int lim) {int c, i;for (i = 0; i < lim - 1 && (c = getchar()) != EOF && c != '\n'; ++i) {s[i] = c;}   if (c == '\n') {s[i] = c;++i;}   s[i] = '\0';return i;
}/** 拷贝数组*/
void copy(char *to, char *from) {int i = 0;while ((to[i] = from[i]) != '\0') {++i;}
}int main() {int len;int max = 0;char line[MAXLINE];char longest[MAXLINE];while ((len = getline_s(line, MAXLINE)) > 0) {if (len > max) {max = len;copy(longest, line);}   }   if (max > 0) {printf("%s\n", longest);}   return 0;
}

// strlen简化版本
int strlen(const char *str) {int i = 0;while (str[i] != '\0') {++i;}return i;
}

// 将字符串转换成整数值
int atoi(char *s) {int i;int result = 0;for (i = 0; s[i] != '\0'; ++i) {if (s[i] >= '0' && s[i] <= '9') {result = result * 10 + (s[i] - '0');}}return result;
}

unsigned long next = 1;
//返回取值0~32767之间的伪随机数
int rand(void) {next = next * 110531245 + 12345;// ？return (unsigned int)(next / 65535) % 32768;
}// 随机数种子
void srand(unsigned int seed) {next = seed;
}

 1 // 从字符串s中删除字符c
 2 void squeeze(char *s, int c) {
 3     int i, j;
 4     for (i = j = 0; s[i] != '\0'; ++i) {
 5         if (s[i] != c) {
 6             s[j++] = s[i];
 7         }
 8     }
 9     s[j] = '\0';
10 }

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 1 // 将字符串t连接到字符串s的尾部， 假设s有足够的空间
 2 void strcat(char *s, char *t) {
 3     int i, j;
 4     i = j = 0;
 5     while (s[i] != '\0') {
 6         i++;
 7     }
 8
 9     while ((s[i++] = t[j++]) != '\0');
10 }

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 1 // 希尔排序
 2 void shellsort(int *v, int n) {
 3     int gap;
 4     int i, j;
 5     int temp;
 6     for (gap = n / 2; gap > 0; gap /= 2) {
 7         for (i = gap; i < n; ++i) {
 8             for (j = i - gap; j >= 0 && v[j] > v[j + gap]; j -= gap) {
 9                 temp = v[j];
10                 v[j] = v[j + gap];
11                 v[j + gap] = temp;
12             }
13         }
14     }
15 }

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 1 // 使用递归打印十进制数n
 2 void printd(int n) {
 3     if (n < 0) {
 4         putchar('-');
 5         n = -n;
 6     }
 7
 8     if (n / 10) {
 9         printd(n / 10);
10     }
11
12     putchar(n % 10 + '0');
13 }

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// 快速排序
void qsort(int *v, int left, int right) {int i, last;if (left >= right) return ;swap(v, left, (left + right) / 2); last = left;for (i = left + 1; i <= right; ++i) {if (v[i] < v[left]) {swap(v, ++last, i); }   }   swap(v, left, last);qsort(v, left, last - 1); qsort(v, left + 1, right);
}

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1 // 该过程没有进行字符串的复制，而只是涉及到指针操作
2 // c语言没有提供将整个字符串作为一个整体进行处理的运算符
3 cha *pmessage;
4 pmessage = "now is the time";

1 // 定义一个数组
2 char amessage[] = "now is the time";
3
4
5 // 定义一个指针
6 char *pmessage = "now is the time";

// 该数组有13个元素，其中每个元素都是指向整型对象的指针
int* daytab[13];// daytab是一个指针，指向具有13个整型元素的一维数组
int (*daytab)[13]; 

1 // Point
2 struct Point {
3    int x;
4    int y;
5 };
6
7 struct Point pt = {320, 200};

1 // 返回对象或者类型占用的存储空间字节数
2 sizeof 对象 or sizeof(类型名)