c - 数组中元素的数量

Question

谁能帮我打印一个循环计算出的结果个数？这是我的代码:

#include <stdio.h>
int
main (void)

{

    int monthly_water_arr[30];
    int x,num_months;
    int count_0=0;
    FILE *in;
    in = fopen("water.txt","r");
    x=0;
    while (!feof(in))
    {
        fscanf(in,"%d",&monthly_water_arr[x]);
        x++;
        ;
    }
    printf("count is %d\n", count_0);
    printf(" Numbers read from file are:\n");
    for (x=0;x<30;x++){
        printf("%d\n",monthly_water_arr[x]);
    }
    num_months = sizeof(monthly_water_arr)/ sizeof(monthly_water_arr[0]);
    printf("The number of months in file are: %d\n",num_months);
    for (x=0;x<30;x++){
        if(monthly_water_arr[x]>=71 && monthly_water_arr[x]<=80);
        count_0=count_0+1
    }

            return (0);
}

count_0 应该给出两个，但我已经尝试了很多，实际上只有 2 个数字在 71 和 80 之间，每次我只得到 30

Answer 1

你放错了分号:

if(monthly_water_arr[x]>=71 && monthly_water_arr[x]<=80);
count_0=count_0+1

注意 if 后面的分号。这实际上更准确地写为:

if(monthly_water_arr[x]>=71 && monthly_water_arr[x]<=80) //If this,
    ; //Do nothing.
count_0=count_0+1 //Either way, increment count.

不要在 if、for 或 while 语句后放置分号。删除它，使计数增量在 if 内:

if(monthly_water_arr[x]>=71 && monthly_water_arr[x]<=80)
    count_0=count_0+1; //or, more concisely, ++count_0;