Sum of numbers in string

Problem Statement - link #

Given a string str containing alphanumeric characters. The task is to calculate the sum of all the numbers present in the string.

Your Task: The task is to complete the function findSum() which finds and returns the sum of numbers in the string.

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(N)

Examples #

Example 1:

Input:
str = 1abc23
Output: 24
Explanation: 1 and 23 are numbers in the
string which is added to get the sum as
24.

Example 2:

Input:
str = geeks4geeks
Output: 4
Explanation: 4 is the only number, so the
sum is 4.

Constraints #

• 1 <= length of the string <= 10^5
• Sum of Numbers <= 10^5

Solutions #

class Solution{
    public:
    //Function to calculate sum of all numbers present in a string.
    int findSum(string str)
    {
    	
    	// Your code here
    	int num = 0, sum = 0;
    	for(int i=0; i<str.size(); i++){
    	    if( '0' <= str[i] && str[i] <= '9')
    	        num = num*10 + (str[i]-'0') ;
    	    else { sum += num; num = 0; }
    	}
    	sum+=num;
    	return sum;
    	
    }
};