Calculate sum of all numbers present in a string

Given a string containing alphanumeric characters, calculate sum of all numbers present in the string.

Input:  1abc23
Output: 24

Input:  sudhakar4sudhakar
Output: 4

Input:  1abc2x30yz67
Output: 100

Input:  123abc
Output: 123

The only tricky part in this question is multiple consecutive digits and considering as one number.
The idea is very simple. We scan each character of the input string and if a number is formed by consecutive characters of the string, we increment the result by that amount.
Below is its  implementation –

#include <iostream> using namespace std; / int findSum(string str) {     // A temporary string     string temp = "";     // holds sum of all numbers present in the string     int sum = 0;          for (char ch: str)     {         // if current character is a digit         if (isdigit(ch))             temp += ch;         // if current character is an alphabet         else         {             // increment sum by number found earlier             // (if any)             sum += atoi(temp.c_str());             // reset temporary string to empty             temp = "";         }     }     // atoi(temp.c_str()) takes care of trailing     // numbers     return sum + atoi(temp.c_str()); } // Driver code int main() {     // input alphanumeric string     string str = "12abc20yz68";     cout << findSum(str);     return 0; }

Output:

100

Time complexity of above solution is O(n) where n is length of the string.