小弟刚学C 现被几个题目难住了，请高手帮帮忙：

1. 编写计算n的阶乘的程序。



2.编写一个两位十进制数AB，其中AB×AB＝403，求A和B的值的程序。



再有小弟编的这个程序错的哪？

mian()

{ char op;

  printf("Please input a operator:\n");

  scanf("%c",&op);

  switch(op)

  { case 'a':

      printf("op=%c  %c\n",op,"American");

      break;

    case 'b':

      printf("op=%c  %c\n",op,"Britain");

      break;

    case 'c':

      printf("op=%c  %c\n",op,"China");

      break;

    case 'd':

      printf("op=%c  %c\n",op,"Denmark");

      break;

    default:

      printf("Other");

  }

}

//好久没来了,帮你做了下,练下手感, //1. 编写计算n的阶乘的程序。

/* #include <stdio.h>

double Jie_cheng(int);

double Jie_Cheng(int number) { if(number==1) return 1; else return number*Jie_Cheng(number-1); }

int main() { int number; printf("please enter the number:\n"); scanf("%d",&number); printf("%d!=%.lf.\n",number,Jie_Cheng(number)); return 0; } */

//2.编写一个两位十进制数AB，其中AB×BA＝403，求A和B的值的程序 /* #include <stdio.h>

void process(int number) { int i; int j; int flag=1; for(i=1;i<10;i++) { for(j=1;j<10;j++) { if((i*10+j)*(j*10+i)==number) { flag=0; printf("%d=%d*%d\n",number,i*10+j,j*10+i); } } } if(flag==1) printf("Don't exist the number.\n"); }

int main() { int number; do { printf("please enter the number(100<=number<=9801).\n"); scanf("%d",&number); }while(number<100||number>9801); process(number); return 0; } */

#include <stdio.h>

int main() { char op; printf("Please input a operator:\n"); scanf("%c",&op); switch(op) { case 'a': printf("op=%c %s\n",op,"American"); break; case 'b': printf("op=%c %s\n",op,"Britain"); break; case 'c': printf("op=%c %s\n",op,"China"); break; case 'd': printf("op=%c %s\n",op,"Denmark"); break; default: printf("Other"); } return 0; }