C语言控制语句: 循环

while循环

#include "stdio.h"
int main(void){
    long num;
    long sum = 0L;
    int status;
    printf("请输入status的值:");
    status = scanf("%ld",&num);
    printf("status:%d\n",status);
    /* while (status == 1)/*== 意思是"等于"*/
    /*{
        sum = sum + num;
        printf("next status:");
        status = scanf("%ld",&num);
        printf("status:%d\n",status);
    } */
    while (scanf("%ld",&num) == 1)
    {
        sum = sum + num;
        printf("next status:");
        status = scanf("%ld",&num);
        printf("status:%d\n",status);
    }
    printf("%-10ld",sum);
    return 0;
}

终止循环

/*when.c  -- 终止循环*/
#include "stdio.h"
int main(void){
    int n = 5;
    while(n-- > 0){
        printf("%-5d",n);
    }
    return 0;
}

/*while1.c  -- 注意花括号的使用*/
#include "stdio.h"
int main(void){
    int n = 5;
    while(n-- > 0)
        printf("%-5d",n); //只执行这一条语句
    printf("end\n");
    return 0;
}

注意分号位置

/*while2.c -- 注意分号的位置*/
#include "stdio.h"
int main(void){
    int n = 5;
    while(n-- > 0);
        printf("%d\n",n);
    return 0;
}

浮点比较

/*cmpflt.c  --  浮点数比较*/
#include "stdio.h"
int main(void){
    const double ANSWER = 3.1415926;
    double response;
    printf("输入response(double):");
    scanf("%lf",&response);
    while((response - ANSWER) > 0.0001){
        printf("Try again!\n");
        scanf("%lf",&response);
    }
    return 0;
}

其他真值

/*truth.c -- 其他真值*/
#include "stdio.h"
void main(void){
    char c = 'C';
    while(c == 'C'){
        printf("已经进入循环,请输入c的值:");
        scanf("%c",&c);
        printf("%-5c,%d",c,sizeof(c));
    }
}

新的_Bool类型

/*boolean.c -- 使用_Bool类型的变量*/
#include "stdio.h"
int main(void){
    long num;
    long sum = 0L;
    _Bool input_is;
    printf("是否开始循环?(1 or 0):");
    scanf("%ld",&input_is);
    while(input_is == 1){
        printf("num的值:");
        scanf("%ld",&num);
        sum = sum + num;
        printf("是否继续循环?(1 or 0):");
        scanf("%ld",&input_is);
    }
    printf("%ld",sum);
}

优先级和关系运算符

运算符优先级

for循环

/*boolean.c -- 使用_Bool类型的变量*/
#include "stdio.h"
int main(void){
    long num;
    long sum = 0L;
    _Bool input_is;
    printf("是否开始循环?(1 or 0):");
    scanf("%ld",&input_is);
    while(input_is == 1){
        printf("num的值:");
        scanf("%ld",&num);
        sum = sum + num;
        printf("是否继续循环?(1 or 0):");
        scanf("%ld",&input_is);
    }
    printf("%ld",sum);
}

逗号运算符

/*postage.c -- 逗号运算符*/
#include "stdio.h"
int main(void){
    int i,j;
    for(i=0,j = 0;i+j<10;i++,j++)
        printf("i=%d,j=%d,i+j=%d\n",i,j,i+j);
    printf("i=%d,j=%d,i+j=%d\n",i,j,i+j);
    return 0;
}

当Zone遇到for循环

/*zeno.c -- 求序列的和*/
#include "stdio.h"
int main(void){
    int ct;
    double time,power_of_2;
    int limit;
    printf("limit的值:");
    scanf("%d",&limit);
    for(time=0, power_of_2=1, ct=1; ct <= limit;ct++, power_of_2=2.0){
        time += 1.0 / power_of_2;
        printf("time=%f,ct=%d\n",time,ct);
        // printf("power_of_2=%f\n",power_of_2);
    }
    return 0;
}

出口条件循环: do..while()

/*do_while.c -- 出口条件循环*/
#include "stdio.h"
int main(void){
    int i = 0;
    int a = 0;
    do{
        printf("a=%d\n",++a);
        if(a < 5)
            i++;
    }while(i == 0);
    return 0;
}

嵌套循环

/*rowsl.c -- 嵌套循环*/
#include "stdio.h"
int main(void){
    for(int i=1;i<10;i++){
        printf("i=%d\n",i);
        for(int j=1; j<=i; j++){
            printf("i=%d,j=%d,i*j=%d\n",i,j,i*j);
        }
    }
}

数组

/*scores_in.c -- 使用循环遍历数组*/
#include "stdio.h"
#define SIZE 10
void arrSum();
int main(void){
    arrSum();
    return 0;
}
void arrSum(){
    int arrInt[SIZE] = {1,32,56,35,10};
    for(int i=0; i<SIZE;i++){
        if(i == 5){
            break;
        }
        printf("arrInt[%d]:%5d\n",i,arrInt[i]);
    }
}