C基礎（16——20）

#include <stdio.h>
#include <stdlib.h>

void test()
{
                 int i=0;
                 int sum=1;

                 for(i=9;i>0;i--)
                {
                                sum=(sum+1)*2;
                }

                printf( "the total=%d\n",sum);
}
int main()
{
                test();
                system( "pause");
                 return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

void test()
{
                 int i=0;
                 float sum=0;

                 for(;i<100;i++)
                {
                                sum+=(pow(-1.0,i))/(i+1);
                }
                printf( "sum=%f\n",sum);
}
int main()
{
                test();
                system( "pause");
                 return 0;
}

#include <stdio.h>
#include <stdlib.h>

void test()
{
                 int tmp=1;
                 int sum=0;

                 for(int i=1;i<=20;i++)
                {
                                tmp=i*tmp;
                                sum+=tmp;
                }

                printf( "sum=%d\n",sum);
}
int main()
{
                test();
                system( "pause");
                 return 0;
}

#include <stdio.h>
#include <stdlib.h>

void test()
{
                 int m=0;
                printf( "Please input the figure:" );
                scanf( "%d",&m);
                 int n=0;  //反轉後的數
                 int tmp=m;

                 while(tmp)
                {
                                n=n*10+tmp%10;
                                tmp/=10;
                }

                 if(n==m)
                                printf( "Yes\n");
                 else
                                printf( "No\n");
}
int main()
{
                test();
                system( "pause");
                 return 0;
}

      

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void test()
{
                 char* str="12bn21" ;
                 char* start=str;
                 char* end=str+strlen(str)-1;   //注意此處end的定義

                 while(start<end)
                {
                                 if(*start==*end)
                                {
                                                start++;
                                                end--;
                                }
                                 else
                                {
                                                printf( "%s\n",str);
                                                printf( "No\n");
                                                 return;
                                }
                }
                printf( "%s\n",str);
                printf( "Yes\n");
}
int main()
{
                test();
                system( "pause");
                 return 0;
}

改爲char* str="123abnba321" ;  結果爲

sizeof：運算符，計算字節數

strlen：函數，計算字符串長度