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Hackerrank > CPP > Strings



C++ provides a nice alternative data type to manipulate strings, and the data type is conveniently called string. Some of its widely used features are the following:
  • Declaration:
    string a = "abc";
  • Size:
    int len = a.size();
  • Concatenate two strings:
    string a = "abc";
    string b = "def";
    string c = a + b; // c = "abcdef".
  • Accessing <span class="MathJaxPreview">ith element:_
    string s = "abc";
    char   c0 = s[0];   // c0 = 'a'
    char   c1 = s[1];   // c1 = 'b'
    char   c2 = s[2];   // c2 = 'c'
    s[0] = 'z';         // s = "zbc"
P.S.: We will use cin/cout to read/write a string.
Input Format
You are given two strings, a and b, separated by a new line. Each string will consist of lower case Latin characters ('a'-'z').
Output Format
In the first line print two space-separated integers, representing the length of aand b respectively. In the second line print the string produced by concatenatinga and b (a+b). In the third line print two space-separated strings, a and baand b are the same as a and b, respectively, except that their first characters are swapped.
Sample Input
Sample Output
4 2
ebcd af
  • a=abcd"
  • b=ef"
  • |a|=4
  • |b|=2
  • a+b=abcdef"
  • a=ebcd"
  • b=af"
#include <iostream>
#include <string>
using namespace std;
int main() {
    string a, b;
    cin >> a;
    cin >> b;
    cout << a.size() << " " << b.size() << "\n"; // Line 1
    cout << a << b << "\n"; // Line 2
    // Line 3
    if (b.size()) {
        cout << b[0];
    for (int i = 1; i < a.size(); i++) {
        cout << a[i];
    cout << " ";
    if (a.size()) {
        cout << a[0];
    for (int i = 1; i < b.size(); i++) {
        cout << b[i];
    cout << "\n";
    return 0;


stringstream is a stream class to operate on strings. It basically implements input/output operations on memory (string) based streams. stringstream can be helpful in different type of parsing. The following operators/functions are commonly used here
  • Operator >> Extracts formatted data.
  • Operator << Inserts formatted data.
  • Method str() Gets the contents of underlying string device object.
  • Method str(string) Sets the contents of underlying string device object.
Its header file is sstream.
One common use of this class is to parse comma-separated integers from a string (e.g., "23,4,56").
stringstream ss("23,4,56");
char ch;
int a, b, c;
ss >> a >> ch >> b >> ch >> c;  // a = 23, b = 4, c = 56
You have to complete the function vector parseInts(string str)str will be a string consisting of comma-separated integers, and you have to return a vector of int representing the integers.
Note If you want to know how to push elements in a vector, solve the first problem in the STL chapter.
Input Format
The first and only line consists of n integers separated by commas.
Output Format
Print the integers after parsing it.
P.S.: I/O will be automatically handled. You need to complete the function only.
Sample Input
Sample Output
#include <sstream>
#include <vector>
#include <iostream>
using namespace std;
vector<int> parseInts(string str) {
    stringstream ss(str);
    vector<int> result;
    char ch;
    int currentNumber;
    while(ss >> currentNumber) {
        ss >> ch;
    return result;
int main() {
    string str;
    cin >> str;
    vector<int> integers = parseInts(str);
    for(int i = 0; i < integers.size(); i++) {
        cout << integers[i] << "\n";
    return 0;


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