用 if -else 语句 写的程序结果为什么会输出两次？以下是原代码：

Question

#include<stdio.h>
#include<string.h>
int main(){
int i;
char string[100],copy[100];

for(i=0;;i++){
    printf("print your string: ");
    scanf("%s",string);puts(string);
    for(i=0;i<256;i++){
        strcpy(copy,string);
        if(copy[i] !='0' )
            continue;
         else if(copy[i]=='0')
            printf("Invalid input!\n");
    }
    char z;
    printf("do you want to continue? choose Yes or No ['Y'or'N']: ");
    scanf("%c",&z);
    if(z=='Y')
        continue;
    else if(z=='N')
        break;
}
printf("Bye.\n");
return 0;

}

图片：

output：
print your string: 0lkvnn;dfu
0lkvnn;dfu
Invalid input!
Invalid input!
do you want to continue? choose Yes or No ['Y'or'N']: print your string: Y
Y
do you want to continue? choose Yes or No ['Y'or'N']: print your string: N
N
do you want to continue? choose Yes or No ['Y'or'N']: print your string:
（后面没往下打了）

Answer 1

因为最后一个scanf 接收了上面的输入之后的换行符。
你可以在最后一个scanf之前和之后，都加个getchar()接收一下换行符