Cin/Scanf in For loop-CodePudding

I have tried using cin in a for loop, as such

int main() {
  int var1, var2, var3;
  for (int i = 0; i < 10; i  ) {
    std::cin >> var1 >> var2 >> var3;
    // printf("hi\n"); 
  }
}

when I run the code it only reaches cin once, and then cin is no longer called again.

The input should be 10 rows, each of which has 3 integers, such as

and so on

If I uncomment the printf("hi\n");, it will print hi 10 times. Why is this, how can I use cin in a for loop correctly. I have tried using scanf but have reached the same problem.

Thanks!

CodePudding user response：

Thanks everyone for helping, I have figured out the reason. The reason is described by Andreas Wenzel and anastaciu, which was that the input were not integers. Instead of inputting an int for var1, I was inputting a char, but the full code is as shown

int main() {
int var1; int var2; int var3;
for(int i = 0; i < 3; i  ) {
 std::cin >> var1 >> var2 >> var3;
} 
return 0;
}

An example input which would cause an error (still not sure what this specific error is), would result in this output

H 2 3
hi
hi
hi

But using all int as inputs worked fine.

CodePudding user response：

cin in a for loop is correctly std::cin >> var1 >> var2 >> var3; but input var1 var2 var3 it's not the same line when you write new line you pass second argument for example all input this 1 2 3 is var1 it's not (var1 = 1 var2 = 2 var3 = 3)