加密算法：每一字符与15异或实现低四位取反高四位保持不变。#include stdlibh#include stringh#define LENGTH 81int mainvoid char p; char q; p = charmallocsizeofcharLENGTH; strcpyp I am a student!; ; while p

加密算法实现代码如下：

#include <stdlib.h> #include <string.h> #define LENGTH 81

int main(void) { char *p; char q;
p = (char)malloc(sizeof(char)LENGTH); strcpy(p, "I am a student!"); q = (char)malloc(sizeof(char)*LENGTH); char temp; int high, low; while (*p) {
temp = *p ^ 15; high = (temp & 0xf0) >> 4; low = (temp & 0x0f) ^ 0x0f; *q = ((high << 4) | low); p++; q++; } *q = '\0'; puts(q-strlen("I am a student!")); free(p); free(q); return 0;