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Author: Tianle Yuan

STDIN and STDOUT⚓︎

Keywords: Standard I/O

Situation⚓︎

Below is the typical question format:

Question type
C++
#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    return 0;
}

STDIN⚓︎

The situation of STDIN can be separated into below types:

Load element⚓︎

Load element
C++
......
int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */ 
    char a;
    int b;
    string c;
    cin >> a >> b >> c;
    cout << a << " " << b << " " << c;
    //input: x 1 7g qt
    //output: x 1 7g
    return 0;
}
Warning! Space , Enter , and Tab
  • >> will filter(auto jump) all the input unseen characters.
  • If input type is string or char[], the character loading will stop when meet the unseen characters.
C++
......
int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */ 
    //WAY1: use "int cin.get()"
    int cha,chb,chc;
    cha = cin.get();
    chb = cin.get();
    chc = cin.get();
    cout << cha << " " << chb << " " << chc << endl;
    //input: a b c
    //output: 97(a) 32(space) 98(b)

    //WAY2: use "istream& cin.get(char& var)"
    char a[4] = {};
    cin.get(a, 4);

    //input: a b c
    //output: a_b_ ("_" means space)

    return 0;
}
Warning!
  • Even though get() returns int, the return value represents ASCll value.
    • Successful read: return the of the ASCll value character. When an end-of-file character is encountered, return EOF or -1.
  • The get() function reads characters from the buffer WITHOUT ignoring the separator.

Load single line⚓︎

Load single line
Text Only
```cpp
......
int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */ 
    char a[10] = {};
    char b[10] = {};
    string line;
    cin.getline(a,3);         //read line until: length (including 'enter') == 3
    cin.getline(b,5,'\n');    //indicate end symbol: '\n'
    getline(cin,line);        //read the whole line into string including space.
    cout << a << "," << b << "," << line; 

    //input:ak 
    //      ksks
    //      cmas;ckmaslc
    //output: ak,ksks,cmas;ckmaslc

    return 0;
}
```

Load multiple line⚓︎

Load multiple line
C++
......
int main() {
    vector<int> a;
    int temp;

    cin >> temp;
    a.push_back(temp);
    while (cin.get() != '\n') 
    {
        cin >> temp;
        a.push_back(temp);
    }
    //input: 1 2 3
    //output: 1 2 3
    return 0;
}
C++
......
vector<int> a;
string line, word;
int main() {
    getline(cin, line);
    istringstream record(line);
    while (record >> word)
    {
        a.push_back(atoi(word.c_str()));
    }
}

STDOUT⚓︎

References:⚓︎

Last update: January 30, 2023 22:36:05
Created: November 7, 2022 23:10:40

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