int a=0； while (scanf("%d", &a) != EOF) { } 这个也会死循环

这段代码描述的是使用`scanf`函数从标准输入读取整数到变量`a`，并且在一个`while`循环中持续进行，直到遇到文件结束符(EOF)才停止。如果用户不再输入任何数据或者直接按回车而不是输入数字，`scanf`会返回非零值（除了EOF），条件判断`scanf("%d", &a) != EOF`将始终满足，导致进入死循环。

这是因为`scanf`默认等待用户输入一个整数，如果没有输入或者输入了非数字字符（如空格、换行或制表符等），它不会更新`a`的值，而是继续等待新的输入。当用户没有提供有效的输入，循环就无法自然终止，形成死循环。

为了避免这种情况，通常会在循环内部添加一个条件检查`a`是否已经被赋值，或者在读取完数据后明确地退出循环，例如：

int a = 0;
while (scanf("%d", &a) == 1) {
    // 处理读入的数据
}
// 检查并处理可能未读完的剩余输入
if (feof(stdin)) {
    printf("No more input.\n");
} else {
    printf("Unexpected input format.\n");
}

相关问题

#include <stdio.h> #include <stdlib.h> int findHead(FILE * ,int); int findLast(FILE * ,int); void deleteState(FILE **,int * ,int *); void deleteLine(FILE **,int ,int ); int main(){ FILE * fp = fopen("dict.dic","r"); int start,end; if(fp != NULL){ int a,b,c,d,e; fscanf(fp,"%d",&a); fscanf(fp,"%d",&b); fscanf(fp,"%d",&c); fscanf(fp,"%d",&d); fscanf(fp,"%d",&e); int mode; scanf("%d",&mode); switch (mode) { case 1: rewind(fp); start = findHead(fp,5); rewind(fp); end = findLast(fp,a); break; case 2: rewind(fp); start = findHead(fp,a); rewind(fp); end = findLast(fp,b); break; case 3: rewind(fp); start = findHead(fp,b); rewind(fp); end = findLast(fp,c); break; case 4: rewind(fp); start = findHead(fp,c); rewind(fp); end = findLast(fp,d); break; case 5: rewind(fp); start = findHead(fp,d); rewind(fp); end = findLast(fp,e); break; default: printf("??"); break; } rewind(fp); while(ftell(fp)<start) fgetc(fp); while(ftell(fp) != end){ int currentch = fgetc(fp); int flag = 1; if(currentch == '/' ){ int nextch = fgetc(fp); if(nextch == ''){ while(flag && ftell(fp) != end){ currentch = fgetc(fp); while(currentch == '' && ftell(fp) != end){ currentch = fgetc(fp); if(currentch == '/' && ftell(fp) != end) flag = 0; } } } else if(nextch == '/'){ while(currentch != '\n'){ currentch = fgetc(fp); } } else { printf("%c",currentch); currentch = nextch; } } if(ftell(fp) != end && flag) printf("%c",currentch); } } fclose(fp); return 0; } int findHead(FILE * fp,int line){ int ch = 0; while(line-- && ch != EOF){ ch = fgetc(fp); while(ch != '\n' && ch != EOF){ ch = fgetc(fp); } } return ftell(fp); } int findLast(FILE * fp,int line){ int ch = 0; while(line-- && ch != EOF){ ch = fgetc(fp); while(ch != '\n' && ch != EOF){ ch = fgetc(fp); } } return ftell(fp); }将子函数并到主函数里

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

int main(){
FILE * fp = fopen("dict.dic","r");
int start,end;
if(fp != NULL){
int a,b,c,d,e;
fscanf(fp,"%d",&a);
fscanf(fp,"%d",&b);
fscanf(fp,"%d",&c);
fscanf(fp,"%d",&d);
fscanf(fp,"%d",&e);
int mode;
scanf("%d",&mode);
switch (mode) {
case 1:
rewind(fp);
start = findHead(fp,5);
rewind(fp);
end = findLast(fp,a);
break;
case 2:
rewind(fp);
start = findHead(fp,a);
rewind(fp);
end = findLast(fp,b);
break;
case 3:
rewind(fp);
start = findHead(fp,b);
rewind(fp);
end = findLast(fp,c);
break;
case 4:
rewind(fp);
start = findHead(fp,c);
rewind(fp);
end = findLast(fp,d);
break;
case 5:
rewind(fp);
start = findHead(fp,d);
rewind(fp);
end = findLast(fp,e);
break;
default:
printf("??");
break;
}
rewind(fp);
while(ftell(fp)<start)
fgetc(fp);
while(ftell(fp) != end){
int currentch = fgetc(fp);
int flag = 1;
if(currentch == '/' ){
int nextch = fgetc(fp);
if(nextch == '\n'){
while(flag && ftell(fp) != end){
currentch = fgetc(fp);
while(currentch == ' ' && ftell(fp) != end){
currentch = fgetc(fp);
if(currentch == '/' && ftell(fp) != end)
flag = 0;
}
}
}
else if(nextch == '/'){
while(currentch != '\n'){
currentch = fgetc(fp);
}
}
else {
printf("%c",currentch);
currentch = nextch;
}
}
if(ftell(fp) != end && flag)
printf("%c",currentch);
}
}
fclose(fp);
return 0;
}

int findHead(FILE * fp,int line){
int ch = 0;
while(line-- && ch != EOF){
ch = fgetc(fp);
while(ch != '\n' && ch != EOF){
ch = fgetc(fp);
}
}
return ftell(fp);
}

int findLast(FILE * fp,int line){
int ch = 0;
while(line-- && ch != EOF){
ch = fgetc(fp);
while(ch != '\n' && ch != EOF){
ch = fgetc(fp);
}
}
return ftell(fp);
}

#include<stdio.h> int main(){ int x; int i=0,j=0; while((scanf("%d",&x))!=EOF){ int a[x][x]; int flag=0; int num=x; for(i=0;i<x;i++){ for(j=0;j<x;j++){ scanf("%d",&a[i][j]); if(a[i][j]==1){ flag=1; } } if(flag){ num--; flag=0; } } printf("%d\n",num); } return 0; }转成python语言

以下是转换成Python语言的代码：

while True:
    try:
        x = int(input())
        i = 0
        j = 0
        a = []
        flag = 0
        num = x
        for i in range(x):
            row = list(map(int, input().split()))
            a.append(row)
            if 1 in row:
                flag = 1
            if flag:
                num -= 1
                flag = 0
        print(num)
    except:
        break

注意：Python中没有EOF的概念，可以通过try-except语句来实现读入数据的结束判断。此外，Python中二维数组可以用列表嵌套列表的形式来表示。