Given a number as a string where some of the digits are replaced by a ‘$’, the task is to generate all possible number by replacing the ‘$’ with any of the digits from the given string.
Examples:
Input: str = “23$$”
Output:
2322
2323
2332
2333Input: str = “$45”
Output:
445
545
Approach:
- Find all the combinations of the string by replacing the character $ with any of the digits of the string, for this check if the current character is a digit if yes then store this character into an array pre[] then recursively find all of its combinations else if current character is a ‘$’ then replace it with the digits stored in the array and recursively find all the combinations.
- To find the all possible numbers initialize array set[] that stores all the possible numbers, to generate numbers take two nested loop outer loop is for input string and inner loop is for array set[] that stores all the possible combinations of the numbers. Initialize the boolean flag to check if character of the input string is already present in set[] or not if character of the input string is already present in set[] then set flag = false else if flag is true then move the current character of the input string to set[] and recursively find all the combinations of the input string and store it in the array set[]. Finally print each number from the array set[]
Below is the implementation of the above approach:
// C++ implementation of the approach #include <stdbool.h> #include <stdio.h> #include <string.h> #define MAX 20 #define DIGITS 10 // Array to store all the // possible numbers char set[DIGITS]; // Index to set[] element int end; // Function to find all the combinations // of the string by replacing '$' with // the other digits of the string void combinations(char* num, char* pre, int curr, int lvl) { // Check if current length is less than // the length of the input string if (curr < strlen(num)) { // If current charecter is a digit // then store digit into pre[] and // recursively find all the combinations if (num[curr] >= '0' && num[curr] <= '9') { pre[lvl] = num[curr]; combinations(num, pre, curr + 1, lvl + 1); } // If current charecter is a '$' then replace // it with the other digits of the string and // recursively find all the combinations // Else go to the next charecter and // recursively find all the combinations else if (num[curr] == '$') for (int i = 0; i < end; i++) { pre[lvl] = set[i]; combinations(num, pre, curr + 1, lvl + 1); } else combinations(num, pre, curr + 1, lvl); } // Print the array pre[] else { pre[lvl] = '\0'; printf("%s\n", pre); } } // Function to find all the numbers formed // from the input string by replacing '$' with // all the digits of the input string int findNumUtil(char num[]) { // Array that stores the digits before // the charecter $ in the input string char pre[MAX]; end = 0; // Traverse the input string and check if // the current charecter is a digit // if it is then set flag to true for (int i = 0; i < strlen(num); i++) if (num[i] >= '0' && num[i] <= '9') { bool flag = true; // Check if current character of the input // string is already present in the array set[] // then set flag to false for (int j = 0; j < end; j++) if (set[j] == num[i]) flag = false; // Flag is true then store the charecter // into set[] and recursively find all // the combinations of numbers and store // it in the set[] array if (flag == true) set[end++] = num[i]; } combinations(num, pre, 0, 0); return 0; } // Function to print all the combinations // of the numbers by replacing '$' with // the other digits of the input string int findNum(char* num, int* result_count) { int i; if (num[i]) { result_count[i] = findNumUtil(num); return (result_count[i]); } return 0; } // Driver code int main() { char num[MAX] = "23$$"; int result_count[MAX]; findNum(num, result_count); return 0; } |
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Output:
2322 2323 2332 2333
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