《C和指针》学习笔记[第四章 语句]
4.13问题
1.
它是合法的，执行了加减乘除操作，但没有赋值
2.
x = expression
3.
合法
4.
if 后面用;空语句，或者else的条件该到用if的， 用!就可以.
5.
0
1
2
3
4
5
6
7
8
9
6.
个人感觉都差不多。水平有限
7.
少了{}，while的执行体就是第一个语句
正确的
while ((ch = getchar()) != EOF) { checksum += ch; putchar(ch); } printf("chechsum = %d\n", checksum);
8.
无论条件是否成立，都需要执行一次的环境下
9.
odd
even
odd
odd
even
odd
10.
int main(void) { int i; scanf("%d", &i); for (; i > 0; i--) { printf("\n"); } return EXIT_SUCCESS; }
11.
int main(void) { int x, y, a, b; scanf("%d %d %d %d", &x, &y,&a,&b); if (x < y || a >= b) { printf("WRONG\n"); } else printf("RIGHT\n"); return EXIT_SUCCESS; }
12.
int main(void) { int in_year; int leap_year; scanf("%d", &in_year); if ((in_year % 4 == 0 && in_year % 100 != 0) || in_year % 400 == 0) { leap_year = 1; } else leap_year = 0; printf("leap_year is %d\n", leap_year); return EXIT_SUCCESS; }
13.
#include <stdio.h> #include <stdlib.h> #include <string.h> #include "t_c.h" int main(void) { int in_num; while (scanf("%d", &in_num) != 0) { switch (in_num) { case 1: printf("who\n"); break; case 2: printf("waht\n"); break; case 3: printf("when\n"); break; case 4: printf("where\n"); break; case 5: printf("why\n"); break; default: printf("don't know"); break; } } return EXIT_SUCCESS; }
14.
#include <stdio.h> #include <stdlib.h> #include <string.h> #include "t_c.h" static int full_num = 10; void eat_hamberger(void) { printf("eat one hamberger\n"); full_num--; } int hungry(void) { return full_num; } int main(void) { while (hungry()) { eat_hamberger(); } return EXIT_SUCCESS; }
15.
#include <stdio.h> #include <stdlib.h> #include <string.h> #include "t_c.h" static int full_num = 0; void eat_hamberger(void) { printf("eat one hamberger\n"); full_num--; } int hungry(void) { if (full_num > 0) return 1; else return 0; } int main(void) { do { eat_hamberger(); } while (hungry()); return EXIT_SUCCESS; }
16.
#include <stdio.h> #include <stdlib.h> #include <string.h> #include "t_c.h" int main(void) { int precipitsting; int temperature; scanf("%d%d", &precipitsting, &temperature); if (precipitsting == 1) { if (temperature < 32) printf("snowing\n"); else printf("raining\n"); } else { if (temperature < 60) { printf("cold\n"); } else printf("warm\n"); } return EXIT_SUCCESS; }
4.14编程练习
1.
#include <stdio.h> #include <stdlib.h> #include <string.h> #include "t_c.h" int main(void) { int n = 1; double i = 1, j; while (1) { j = (i + n / i)/2; printf("%d %lf\n",n, j); if ((j - i) < 0.001 && i != 1) { break; } i = j; n++; } return EXIT_SUCCESS; }
2.
int main(void) { int n; int i; int is_prime; for (n = 2; n <= 100; n++) { is_prime = 1; for (i = 2; i <= n/2; i++) { if (n % i == 0) { is_prime = 0; break; } } if (is_prime) { printf("%d ", n); } } printf("\n"); return EXIT_SUCCESS; }
3.
#include <stdio.h> #include <stdlib.h> #include <string.h> #include "t_c.h" int main(void) { int o, p, q; scanf("%d %d %d", &o, &p, &q); if (o + p > q && o + q > p && p + q >o) { if (o == p || p == q || o == q) { if (o == p && p == q) { printf("等边三角形\n"); } else printf("等腰三角形\n"); } else printf("是三角形\n"); } else printf("无法组成三角形\n"); return EXIT_SUCCESS; }
4.
#include <stdio.h> #include <stdlib.h> #include <string.h> #include "t_c.h" void copy_n(char dst[], char src[], int n) { int i; for (i = 0; i < n; i++) { if (src[i] != '\0') { dst[i] = src[i]; } else { dst[i] = '\0'; } } } int main(void) { char dst[100]; char *src = "hello world"; copy_n(dst, src, 5); printf("%s\n", dst); return EXIT_SUCCESS; }
5.
This is the first line. Another line. And another. And another. And another. And another. Still more. Almost done now -- Almost done now -- Another line. Still more. Finished!
// // t_c.c // pointers_on_c // // Created by sidian on 2022/5/27. // #include <stdio.h> #include <stdlib.h> #include <string.h> #include "t_c.h" #define MAX_CHAR 128 int main(void) { char in_line[MAX_CHAR]; char first_line[MAX_CHAR]; char second_line[MAX_CHAR]; while (gets(in_line) != NULL) { if ( !strcmp(second_line, in_line) && strcmp(in_line, first_line)) { printf("%s\n", in_line); } strcpy(first_line, second_line); strcpy(second_line, in_line); } return EXIT_SUCCESS; }
6.
#include <stdio.h> #include <stdlib.h> #include <string.h> #include "t_c.h" int substr(char dst[], char src[], int start, int len){ int i = 0; if ((int) strlen(src) < start - 1 || len < 0) { dst[0] = '\0'; } else{ for (; i < len; i++) { if (src[start + i] != '\0') { dst[i] = src[start +i]; } else{ break; } } dst[i] = '\0'; } return i; } int main(void) { int n; char dst[100]; char *src = "hello"; n = substr(dst, src, 4, 5); printf("%s\nn = %d\n", dst, n); return EXIT_SUCCESS; }
7.
#include <stdio.h> #include <stdlib.h> #include <string.h> #include "t_c.h" void deblank(char string[]) { int i = 0; int move = 0; for (; i < strlen(string); i++) { if (string[i] == ' ' && string[i+1] == ' ') { move++; } else { string[i - move] = string[i]; } } string[i- move] = '\0'; } int main(void) { char src[] = "he l l o e s"; deblank(src); printf("%s\n", src); return EXIT_SUCCESS; }
