请帮我理解这段代码背后的逻辑

Question

I have been doing problems for while loop in c++ and i got stuck on this problem. Googled the answer to see what i had to do but now i dont understand the logic behind it and why it works.

Here is the problem:

A sequence consists of natural numbers and ends with 0. Determine the value of the second largest element in the sequence, that is, the element that will be the largest if you remove the largest element from the sequence.

Examples-> Input 1: 4, 4, 2, 3, 0 Output 1: 4 ; Input 2: 2 1 0 Output 2: 1

This is the code:

#include <iostream>
using namespace std;
int main() {
    int n, max, smax = 0;
    cin >> n;
    max = n;
    while (n != 0) {
        cin >> n;
        if (n > max) {
            smax = max;
            max = n;
        }
        else if (n > smax) {
            smax = n;
        }
    }
    cout << smax;
    return 0;
}

So, from my understanding max is n so the statement if n > max will never be True. Unless value for max resets with each loop and is 0, but then its always going to be true so there is no point for the second if statement.

Im sure i dont understand how the while loop works and i would like for someone to clear it up for me. Thanks in advance.

Answer 1

While loop repeats its body until the given condition become false. It's relatively easy to make an infinite while loop error in code, eg:

int i = 0;
while (i<10){
cout<<"something\n";
}

Please remember to put some operation that will break the loop in the body. This would work:

int i = 0;
while (i<10){
cout<<"something\n";
i++; //equivalent of i=i+1;
}

Try it yourself: https://www.onlinegdb.com/online_c++_compiler This should help to understand the concept.

Your code actually makes no sense to me. You type some numbers and it changes them until you type 0, when it stops. It doesn't even show you the maximum value you typed. I highly recommend to learn something more clear and useful in C++.