Example: Sum Numbers in String in C

// Sum Numbers in String
#include <stdio.h> // Required for printf
#include <string.h> // Required for strlen
#include <ctype.h>  // Required for isdigit

int sumNumbersInString(const char *str) {
    int totalSum = 0;
    int currentNumber = 0;
    int i = 0;

    // Step 1: Iterate through the string character by character
    while (str[i] != '\0') {
        // Step 2: Check if the current character is a digit
        if (isdigit(str[i])) {
            // Step 3: Build the current number by processing consecutive digits
            currentNumber = currentNumber * 10 + (str[i] - '0');
        } else {
            // Step 4: If a non-digit is found, add the accumulated currentNumber to totalSum
            // Then reset currentNumber for the next potential number
            totalSum += currentNumber;
            currentNumber = 0;
        }
        i++; // Move to the next character
    }

    // Step 5: After the loop, add the last accumulated number (if any) to totalSum
    // This handles cases where the string ends with a number
    totalSum += currentNumber;

    return totalSum;
}

int main() {
    // Test Case 1: String with numbers, letters, and symbols
    const char *testString1 = "abc12def3ghi45jkl";
    printf("String: \"%s\"\n", testString1);
    printf("Sum of numbers: %d\n\n", sumNumbersInString(testString1));

    // Test Case 2: String with only numbers
    const char *testString2 = "12345";
    printf("String: \"%s\"\n", testString2);
    printf("Sum of numbers: %d\n\n", sumNumbersInString(testString2));

    // Test Case 3: String with no numbers
    const char *testString3 = "HelloWorld";
    printf("String: \"%s\"\n", testString3);
    printf("Sum of numbers: %d\n\n", sumNumbersInString(testString3));

    // Test Case 4: String with numbers at the beginning and end
    const char *testString4 = "7apples and 10bananas cost 17dollars";
    printf("String: \"%s\"\n", testString4);
    printf("Sum of numbers: %d\n\n", sumNumbersInString(testString4));

    // Test Case 5: Empty string
    const char *testString5 = "";
    printf("String: \"%s\"\n", testString5);
    printf("Sum of numbers: %d\n\n", sumNumbersInString(testString5));
    
    // Test Case 6: String with zero
    const char *testString6 = "The temperature is 0 degrees";
    printf("String: \"%s\"\n", testString6);
    printf("Sum of numbers: %d\n\n", sumNumbersInString(testString6));

    return 0;
}