Replace digit (Editorial)

Read the number $n$ as a string and the digits $a$ and $b$ as characters. Replace all occurrences of character $a$ in the string $n$ with character $b$. Then print the resulting string, removing any leading zeros. If the final string consists only of zeros, print a single zero.

The resulting number may exceed the range of the int type. For example, if n = 1000000000~(10^9), a = 1, b = 9, the result will be 9000000000~(9 \cdot 10^9).

Algorithm implementation

Store the number $n$ as a string in the array $s$.

char s[100];

Read the number $n$ as a string and the digits $a$ and $b$ as characters.

scanf("%s %c %c",s,&a,&b);

Replace all occurrences of character $a$ with character $b$ in the string $s$.

for (i = 0; i < strlen(s); i++)
  if (s[i] == a) s[i] = b;

Convert the string $s$ into a number $res$ of type long long.

res = atoll(s);

Print the answer.

printf("%lld\n", res);

Algorithm implementation — string

Read the number $n$ as a string and the digits $a$ and $b$ as characters.

cin >> s >> a >> b;

Replace all occurrences of character $a$ with character $b$ in the string $s$.

replace(s.begin(), s.end(), a, b);

Convert the string $s$ into a number $res$ of type long long.

res = stoll(s);

Print the answer.

cout << res << endl;

Java implementation

import java.util.*;

public class Main 
{
  public static void main(String[] args) 
  {
    Scanner con = new Scanner(System.in);
    String s = con.next();
    char a = con.next().charAt(0);
    char b = con.next().charAt(0);
    s = s.replace(a,b);
 
    int flag = 0;
    for(int i = 0; i < s.length(); i++)
    if (s.charAt(i) != '0')
    {
      s = s.substring(i);
      flag = 1;
      break;
    }
    if (flag == 0) s = "0";
    System.out.println(s);
    con.close();
  }
}

Python implementation

Read the input data as strings.

s, a, b = input().split()

Replace all occurrences of character $a$ with character $b$ in the string $s$.

s = s.replace(a, b)

Convert the string $s$ into an integer and print the result.

print(int(s))