参考方案:
#include <stdio.h> #include <math.h> #include <stdbool.h> #include <stdlib.h> #include <sys/time.h> //素数判定 筛选法 int main(){ int num = 100; int i, j; //scanf("%d", &num); //getchar(); bool *b; b=(bool *)calloc(num + 1, sizeof(bool)); b[0] = false; for(i = 1; i <= num; i++){ if(i % 2 == 0){ b[i] = false; }else{ b[i] = true; } } for(int i = 3; i <= sqrt(num); i+=2){ if(b[i]){ for(j=i+i; j <= num; j+=i) b[j] = false; } } //输出素数 printf("2,"); for(i = 3; i <= num; i+=2){ if(b[i]){ printf("%d,", i); } } free(b); b=NULL; return 0; }
利用指针实现:
#include <stdio.h> //题目:字符串反转,如将字符串 "www.facesho.com" 反转为"moc.boonur.www"。 void reverse(char *str); int main() { char str[100]; printf("输入字符串:"); fgets(str, sizeof str, stdin); reverse(str); printf("逆序后:%s\n",str); return 0; } void reverse(char *str) { char *p = str, strNew[100]; int i = 0; while (str[i] != '\n') { strNew[i] = str[i]; ++i; } strNew[i] = '\0';//把原字符串末尾置'\0' while (*p != '\n') *(p++) = strNew[--i];//把原字符逆序 *p = '\0';//逆序后末尾置'\0' }
参考方法:
#include<stdio.h> #include<string.h> #include<stdlib.h> void reverse(char *p,int n); int main() { char *a; a=(char *)malloc(sizeof(char)); printf("请输入字符串:"); //gets(a); fgets(a, (sizeof a / sizeof a[0]), stdin); reverse(a,strlen(a)); } void reverse(char *p,int n) { while(n) { printf("%c",*(p+n-1)); n--; } }
#include<stdio.h> #include<string.h> void reverse(char str[], int lenth) { int i = 1, tmp = lenth; for(i = 1; i <= lenth / 2; i++) { *str ^= *(str + tmp - 1); *(str + tmp - 1) ^= *str; *str ^= *(str + tmp - 1); str++; tmp -= 2; } } int main() { char str[100] = {0}; printf("请输入一个字符串:"); //fgets(str, 100, stdin); scanf("%s", str); reverse(str, strlen(str)); printf("%s\n",str); return 0; }
#include<stdio.h> #include<string.h> #define N 80 void reverse(char *str) { int j = strlen(str); int i = 0; j--; while(i < j) { char temp; temp = str[i]; str[i] = str[j]; str[j] = temp; i++; j--; } } int main(void) { char str[N]; memset(str,'\0',sizeof(str)); gets(str); reverse(str); puts(str); return 0; }
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