Extract the Number from the String

JavaView on GFG

Time: O(n)

Space: O(1)

Intuition

Extract all numeric substrings from a string and compute their sum or return them.

Algorithm

1Scan: when digit found, collect consecutive digits to form number. Add to result.

Common Pitfalls

•Handle multi-digit numbers by accumulating. Use isDigit check. Parse each numeric run.

Extract the Number from the String.java

Java

// Approach: Scan string character by character, accumulate digits, parse the resulting number.
// Time: O(n) Space: O(1)
class Solution {
    long ExtractNumber(String sentence) {
        String arr[] = sentence.split(" ");
        long max = -1;
        for (String st : arr) {
            if (st.charAt(0) - '0' >= 0 && st.charAt(0) - '0' <= 9) {
                if (!st.contains("9")) {
                    long convert = Long.parseLong(st);
                    if (convert > max)
                        max = convert;
                }
            }
        }

        return max;
    }
}

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