C++的几个小题目不会，高手帮忙。
1、编写一个字符串加密函数，加密的规则为字符串的每一位等于自身与其后面一位相或的结果，字符串的最后一位与第一位相或，并在主函数中调用测试加密。
2、开发一个小的班级信息系统，模拟几个学生的各种必要信息，信息存储的载体为文件，可以是文本文件，或二进制文件，每个学生的信息用类体表示，对文件的操作推荐用C语言解决，通用性较好。
3、定义一个班级基类，类中的数据成员和成员函数可以自己拟定，而后定义两个子类，每个子类表示一个特殊的班级，即基类为班级的一个抽象，而各子类为定制的每个班级，如信管1和信管2，信管3和信管4，两个子类中的数据成员和方法各不相同，而且与基类的数据成员和方法相比，要有明显的增加，最后在主函数中进行两个班级的对比操作。
高手帮忙。。。谢谢
问题点数：20、回复次数：13Top
1 楼SamuelKevin（曼陀罗）回复于 2006-06-04 16:50:01 得分 0
Program 1:
char c;
int i;
char str[100];
scanf("%s", str);
c=str[0];
while ( str[i+1]!='\0' )
{
str[i] |= str[i+1];
i++;
}
str[i+1] |= c;
是不是这个意思？Top
2 楼bjx13（）回复于 2006-06-04 17:05:38 得分 0
第2个定义一个结构体数组行不行？
struct stud_info
{char name[20];
long num;
int age;
char sex;
float score;
}
stuct stud_info student[30];Top
3 楼xmlf（小弥勒佛）回复于 2006-06-04 18:41:03 得分 0
好像都不对Top
4 楼xmlf（小弥勒佛）回复于 2006-06-06 19:26:46 得分 0
高手帮帮忙。。。Top
5 楼czg516（伟大的程序员从一点一滴做起）回复于 2006-06-06 20:24:52 得分 0
3个加起来，
代码量不小！Top
6 楼MagicCarmack（MagiC++）回复于 2006-06-07 11:53:49 得分 0
这还叫小题目，我不得不称你老大了Top
7 楼diandian82（点点(nothing)）回复于 2006-06-07 12:33:07 得分 0
markTop
8 楼ctu_85（青灯照壁人初睡，冷雨敲窗被未温）回复于 2006-06-12 15:49:55 得分 0
给你个带容错的，好像是大二 时 作的
#include <math.h>
#include <stdio.h>
#include <float.h>
#include <limits.h>
#include <stdlib.h>
#define MAX_RANDOM LONG_MAX // Maximum value of random()
//#define PRINT_GF
//#define PRINT_POLY
//#define PRINT_SYNDROME
#define m 8
#define n 255
#define length 255
#define red 16
#define k 239 //length - red
#define t 8 //red/2
#define t2 16 //2*t
#define init_zero 1
//int d;
int p[10];
int alpha_to[n+1], index_of[n+1], g[red+1];
int recd[length], data[k], b[red];
int numera, era[t2];
//char filename[40], name2[40];
void read_p(void);
void generate_gf(void);
void gen_poly(void);
void encode_rs(void);
//void bpsk_awgn(void);
void decode_rs(void);
int weight(int word);
main()
{
int i;
int biterror, decerror;//, error;
int numerr, errpos[t], errval[t];
read_p(); // Read m */
generate_gf(); // Construct the Galois Field GF(2^m) */
printf("--> This is an RS(%d,%d,%d) code over GF(2^%d), t = %d\n",
length, k, red+1, m, t);
printf(" with zeros: ");
for (i=0;i<t2;i++) printf("%d ", init_zero+i);
printf("\n\n");
gen_poly(); // Compute the generator polynomial of RS code */
// Randomly generate DATA */
for (i = 0; i < k; i++)
data[i] = (rand()>>10) % n;
encode_rs(); // encode data */
// Codeword is c(X) = data(X)*X**(length-k)+ b(X)
for (i = 0; i < length - k; i++) recd[i] = b[i];
for (i = 0; i < k; i++) recd[i + length - k] = data[i];
//for (i = 0; i < length; i++) recd[i] = 0;
// Introduce errors and erasures at will ...
/* CHANNEL NOISE: Read errors and erasures */
printf("Number of errors, e: "); scanf("%d", &numerr);
if (numerr)
for (i=0; i<numerr; i++)
{
printf("position: "); scanf("%d", &errpos[i]); // as power of alpha
printf("value: "); scanf("%d", &errval[i]); // as vector
recd[errpos[i]] ^= errval[i];
}
printf("Number of erasures, b: "); scanf("%d", &numera);
if (numera)
for (i=0; i<numera; i++)
{
printf("position: "); scanf("%d", &era[i]); // as power of alpha
recd[era[i]] = 0;
}
printf("\n\nRec =");
for (i=0; i<length; i++) {
printf("%4d ", index_of[recd[i]]);
}
printf("\n ");
for (i=0; i<length; i++) {
printf("%4d ", recd[i]);
}
printf("\n");
decode_rs(); // DECODE received codeword recv[] */
// DECODING ERRORS? we compare only the data portion
decerror = 0;
biterror = 0;
for (i = length-k; i < length; i++)
if (data[i-length+k] != recd[i])
{
decerror++;
biterror += weight(data[i-length+k]- recd[i]);
}
}
Top
9 楼ctu_85（青灯照壁人初睡，冷雨敲窗被未温）回复于 2006-06-12 15:50:23 得分 0
void read_p()
// Read m, the degree of a primitive polynomial p(x) used to compute the
// Galois field GF(2**m). Get precomputed coefficients p[] of p(x). Read
// the code length.
{
int i; //, ninf;
printf("\nSimulation of RS codes \n");
for (i=1; i<m; i++)
p[i] = 0;
p[0] = p[m] = 1; //LSB First
if (m == 2) p[1] = 1; //111
else if (m == 3) p[1] = 1; //1101
else if (m == 4) p[3] = 1; //11001
// else if (m == 4) p[1] = 1; // Commented out to match example p. 68
else if (m == 5) p[2] = 1; //101001
else if (m == 6) p[1] = 1; //1100001
else if (m == 7) p[1] = 1; //10010001
else if (m == 8) p[2] = p[3] = p[4] = 1; //101110001
else if (m == 9) p[4] = 1; //1000100001
else if (m == 10) p[3] = 1; //10010000001
else if (m == 11) p[2] = 1;
else if (m == 12) p[3] = p[4] = p[7] = 1;
else if (m == 13) p[1] = p[3] = p[4] = 1;
else if (m == 14) p[1] = p[11] = p[12] = 1;
else if (m == 15) p[1] = 1;
else if (m == 16) p[2] = p[3] = p[5] = 1;
else if (m == 17) p[3] = 1;
else if (m == 18) p[7] = 1;
else if (m == 19) p[1] = p[5] = p[6] = 1;
else if (m == 20) p[3] = 1;
printf("Primitive polynomial of GF(2^%d), (LSB first) p(x) = ",m);
//n = 1;
for (i = 0; i <= m; i++)
{
//n *= 2;
printf("%1d", p[i]);
}
//printf("\n");
//n = n / 2 - 1;
}
void generate_gf()
// generate GF(2^m) from the irreducible polynomial p(X) in p[0]..p[m]
//
// lookup tables: log->vector form alpha_to[] contains j=alpha**i;
// vector form -> log form index_of[j=alpha**i] = i
// alpha=2 is the primitive element of GF(2^m)
{
register int i, mask;
mask = 1;
alpha_to[m] = 0;
for (i=0; i<m; i++)
{
alpha_to[i] = mask;
index_of[alpha_to[i]] = i;
if (p[i]!=0)
alpha_to[m] ^= mask;
mask <<= 1;
}
index_of[alpha_to[m]] = m;
mask >>= 1;
for (i=m+1; i<n; i++)
{
if (alpha_to[i-1] >= mask)
alpha_to[i] = alpha_to[m] ^ ((alpha_to[i-1]^mask)<<1);
else alpha_to[i] = alpha_to[i-1]<<1;
index_of[alpha_to[i]] = i;
}
index_of[0] = -1;
#ifdef PRINT_GF
printf("Table of GF(%d):\n",n);
printf("----------------------\n");
printf(" i\tvector \tlog\n");
printf("----------------------\n");
for (i=0; i<=n; i++)
printf("%4d\t%4d\t%4d\n", i, alpha_to[i], index_of[i]);
#endif
}
void gen_poly()
// Compute the generator polynomial of the t-error correcting, length
// n=(2^m -1) Reed-Solomon code from the product of (X+alpha^i), for
// i = init_zero, init_zero + 1, ..., init_zero+length-k-1
{
register int i,j;
g[0] = alpha_to[init_zero]; // <--- vector form of alpha^init_zero
g[1] = 1; // g(x) = (X+alpha^init_zero)
for (i=2; i<=length-k; i++)
{
g[i] = 1;
for (j=i-1; j>0; j--)
if (g[j] != 0)
g[j] = g[j-1]^ alpha_to[(index_of[g[j]]+i+init_zero-1)%n];
else
g[j] = g[j-1];
g[0] = alpha_to[(index_of[g[0]]+i+init_zero-1)%n];
}
// convert g[] to log form for quicker encoding
for (i=0; i<=length-k; i++) g[i] = index_of[g[i]];
#ifdef PRINT_POLY
printf("Generator polynomial (independent term first):\ng(x) = ");
for (i=0; i<=length-k; i++) printf("%5d", g[i]);
printf("\n");
#endif
}
Top
10 楼ctu_85（青灯照壁人初睡，冷雨敲窗被未温）回复于 2006-06-12 15:50:39 得分 0
void encode_rs()
// Compute the 2t parity symbols in b[0]..b[2*t-1]
// data[] is input and b[] is output in polynomial form.
// Encoding is done by using a feedback shift register with connections
// specified by the elements of g[].
{
register int i,j;
int feedback;
for (i=0; i<length-k; i++)
b[i] = 0;
for (i=k-1; i>=0; i--)
{
feedback = index_of[data[i]^b[length-k-1]];
if (feedback != -1)
{
for (j=length-k-1; j>0; j--)
if (g[j] != -1)
b[j] = b[j-1]^alpha_to[(g[j]+feedback)%n];
else
b[j] = b[j-1];
b[0] = alpha_to[(g[0]+feedback)%n];
}
else
{
for (j=length-k-1; j>0; j--)
b[j] = b[j-1];
b[0] = 0;
}
}
}
void decode_rs()
{
register int i,j,u,q;
int elp[length-k+2][length-k], d[length-k+2], l[length-k+2], u_lu[length-k+2], s[length-k+1], forney[length-k+2];
int count=0, syn_error=0, tau[t], root[t], loc[t];
int err[length], reg[t+1], aux[t+1], omega[length-k+1], phi[length-k+1], phiprime[length-k+1];
int degphi, ell;
// Compute the syndromes
#ifdef PRINT_SYNDROME
printf("\ns = 0 ");
#endif
for (i=1; i<=t2; i++)
{
s[i] = 0;
for (j=0; j<length; j++)
if (recd[j]!=0)
s[i] ^= alpha_to[(index_of[recd[j]]+(i+init_zero-1)*j)%n];
// convert syndrome from vector form to log form */
if (s[i]!=0)
syn_error=1; // set flag if non-zero syndrome => error
//
// Note: If the code is used only for ERROR DETECTION, then
// exit program here indicating the presence of errors.
//
s[i] = index_of[s[i]];
#ifdef PRINT_SYNDROME
printf("%4d ", s[i]);
#endif
}
if (syn_error) // if syndromes are nonzero then try to correct
{
s[0] = 0; // S(x) = 1 + s_1x + ...
// TO HANDLE ERASURES
if (numera)
// if erasures are present, compute the erasure locator polynomial, tau(x)
{
for (i=0; i<=t2; i++)
{ tau[i] = 0; aux[i] = 0;}
aux[1] = alpha_to[era[0]];
aux[0] = 1; // (X + era[0])
if (numera>1)
for (i=1; i<numera; i++)
{
p[1] = era[i];
p[0] = 0;
for (j=0; j<2; j++)
for (ell=0; ell<=i; ell++)
// Line below added 8/17/2003
if ((p[j] !=-1) && (aux[ell]!=0))
tau[j+ell] ^= alpha_to[(p[j]+index_of[aux[ell]])%n];
if (i != (numera-1))
for (ell=0; ell<=(i+1); ell++)
{
aux[ell] = tau[ell];
tau[ell] = 0;
}
}
else {
tau[0] = aux[0]; tau[1] = aux[1];
}
// Put in index (log) form
for (i=0; i<=numera; i++)
tau[i] = index_of[tau[i]]; /* tau in log form */
#ifdef PRINT_SYNDROME
printf("\ntau = ");
for (i=0; i<=numera; i++)
printf("%4d ", tau[i]);
printf("\nforney = ");
#endif
// Compute FORNEY modified syndrome:
// forney(x) = [ s(x) tau(x) + 1 ] mod x^{t2}
for (i=0; i<=n-k; i++) forney[i] = 0;
for (i=0; i<=n-k; i++)
for (j=0; j<=numera; j++)
if (i+j <= (n-k)) // mod x^{n-k+1}
if ((s[i]!=-1)&&(tau[j]!=-1))
forney[i+j] ^= alpha_to[(s[i]+tau[j])%n];
forney[0] ^= 1;
for (i=0; i<=n-k; i++)
forney[i] = index_of[forney[i]];
#ifdef PRINT_SYNDROME
for (i=0; i<=n-k; i++)
printf("%4d ", forney[i]);
#endif
}
else // No erasures
{
tau[0]=0;
for (i=1; i<=n-k; i++) forney[i] = s[i];
}Top
11 楼xmlf（小弥勒佛）回复于 2006-06-17 22:21:30 得分 0
定义一个班级基类，类中的数据成员和成员函数可以自己拟定，而后定义两个子类，每个子类表示一个特殊的班级，即基类为班级的一个抽象，而各子类为定制的每个班级，如信管1和信管2，信管3和信管4，两个子类中的数据成员和方法各不相同，而且与基类的数据成员和方法相比，要有明显的增加，最后在主函数中进行两个班级的对比操作。
高手帮忙。。。谢谢
这个怎么写？Top
12 楼cattlenzq（吃狼的豆腐（不要给分了，散起来真麻烦！））回复于 2006-06-17 23:41:06 得分 0
抽象基类，里面定义虚函数
class baseclass
{
virtual void op1()=0;
virtual void op2()=0;
};
class class1:public baseclass
{
op1(){/*具体操作实现*/}
};
class2也一样重载基类方法，利用基类指针可以指向派生类的指针，然后调用函数，具体自己google下虚函数，任何书理都有介绍的Top
13 楼xmlf（小弥勒佛）回复于 2006-06-21 07:28:11 得分 0
具体的怎么写？Top
