C 控制语句：循环

/对用户输入的整数求和
#include<stdio.h>
int main(void)
{
    long num;
    long sum=0L;//把sum初始化为0
    int status;

    printf("please enter an integer to be summed.");
    printf("q to quit!\n");
//    status=scanf("%ld",&num);//注意有这句和没有这一句的区别。
//    while(status==1)//每次循环都为num获取一个新值，并重置status
    while((status=scanf("%ld",&num))==1)
    {
        sum=sum+num;//累加和
        printf("please enter next integer (q to quit)");
    //    status=scanf("%ld",&num);
    }
    printf("Those integers sum to %ld.\n",sum);
    return 0;
}

关于什么时候退出循环
//关于什么时候退出循环
#include<stdio.h>
int main(void)
{
    int n=5;
    while(n<7)
    {
        printf("n=%d\n",n);
        n++;
        printf("Now n=%d\n",n);
    }
    printf("The loop has finished.\n");
    return 0;
}

浮点数大小的比较，利用fabs()函数
//浮点数大小的比较，利用fabs()函数。
//不能使用关系运算符来比较字符串
//浮点数比较重只能使用<和>，但舍入误差可能造成两个逻辑上相等的数不等
#include<stdio.h>
#include<math.h>//包含fabs()原型
int main(void)
{
    const double ANSWER=3.14159;//定义一个常量
    double response;
    printf("What‘s is the value of pi?\n");
    scanf("%lf",&response);
    while(fabs(response-ANSWER)>0.0001)
    {
        printf("Try again!\n");
        scanf("%lf",&response);
    }
    printf("Close enough!\n");
    return 0;
}

哪些值为真？
//哪些值为真？
#include<stdio.h>
int main(void)
{
    int n=3;
    while(n)
        printf("%2d is true\n",n--);
    printf("%2d is flase.\n",n);
    n=-3;
    while(n)
        printf("%2d is true.\n",n++);
    printf("%2d is flase.\n",n);
    return 0;
}
//所有的非零值都被认为是真，只有0被认为是假。表达式实际上是数

使用for循环实现一个立方表
//使用for循环实现一个立方表
#include<stdio.h>
#define  MAX  20
int main(void)
{
    int n,m;
    printf("n\t n*n*n\n");
    for(n=0;n<=MAX;n++)
        printf("%5d\t%5d\n",n,n*n*n);
    return 0;
}

入口条件循环
//入口条件循环
//应该把do while循环体仅仅用于那些至少需要执行一次循环的情况
#include<stdio.h>
int main(void)
{
    const int secret_code=13;
    int code_entered;

    printf("To enter the triskaidekaphobia therapy club,\n");
    printf("please enter the secret code number:");
    scanf("%d",&code_entered);
    while(code_entered!=secret_code){

        printf("To enter the triskaidekaphobia therapy club,\n");
        printf("please enter the secret code number:");
        scanf("%d",&code_entered);
    }
    
    printf("Congratulations! You are cured!\n");
    return 0;
}

使用循环进行数组的处理
//使用循环进行数组的处理
#include<stdio.h>
#define SIZE  10
#define PAR   72
int main(void)
{
    int index,score[SIZE];
    int sum=0;
    float average;

    printf("Enter %d golf scores:\n",SIZE);
    for(index=0;index<SIZE;index++)
        scanf("%d",score[index]);//输入10个分数 注意这里没有用&
    printf("The scores read in are as follows:\n");
    for(index=0;index<SIZE;index++)
        scanf("5%d",score[index]);//验证输入
    printf("\n");
    for(index=0;index<SIZE;index++)
        sum+=score[index];//求他们的和
    average=(float)sum/SIZE;
    printf("sum of scores=%d,average=%.2f\n",sum,average);
    printf("That‘s a handicap of %.0f.\n",average-PAR);
    return 0;
}

计算数值的整数次幂
//计算数值的整数次幂
#include<stdio.h>
double power(double n,int p);
int main(void)
{
    double x,xpow;
    int exp;

    printf("Enter a number and the positive integer power");
    printf("to witch.\n the number will be raised,Enter q.");
    printf("to quit.\n");

    while(scanf("%lf%d",&x,&exp)==2)
    {
        xpow=power(x,exp);//函数调用
        printf("%.3g to the power %d is %.5g\n",x,exp,xpow);
        printf("Enter next pair of number or q to quit.\n");
    }
    printf("Hope you enjoyed this power trip--bye!\n");
    return 0;
}
//求n的p次幂的函数
double power(double n,int p)//函数定义
{
    double pow=1;
    int i;

    for(i=1;i<=p;i++)
        pow*=n;
    return pow;//返回Pow的值
}