NumberOfDifferentIntegersInAString.cpp

// Source : https://leetcode.com/problems/number-of-different-integers-in-a-string/
// Author : Hao Chen
// Date   : 2021-03-28

/***************************************************************************************************** 
 *
 * You are given a string word that consists of digits and lowercase English letters.
 * 
 * You will replace every non-digit character with a space. For example, "a123bc34d8ef34" will become 
 * " 123  34 8  34". Notice that you are left with some integers that are separated by at least one 
 * space: "123", "34", "8", and "34".
 * 
 * Return the number of different integers after performing the replacement operations on word.
 * 
 * Two integers are considered different if their decimal representations without any leading zeros 
 * are different.
 * 
 * Example 1:
 * 
 * Input: word = "a123bc34d8ef34"
 * Output: 3
 * Explanation: The three different integers are "123", "34", and "8". Notice that "34" is only 
 * counted once.
 * 
 * Example 2:
 * 
 * Input: word = "leet1234code234"
 * Output: 2
 * 
 * Example 3:
 * 
 * Input: word = "a1b01c001"
 * Output: 1
 * Explanation: The three integers "1", "01", and "001" all represent the same integer because
 * the leading zeros are ignored when comparing their decimal values.
 * 
 * Constraints:
 * 
 * 	1 <= word.length <= 1000
 * 	word consists of digits and lowercase English letters.
 ******************************************************************************************************/

class Solution {
private:
    bool isNumber(char ch) {
        return (ch >='0' && ch <='9');
    }
    
public:
    int numDifferentIntegers(string word) {
        word.push_back('z'); // add a char for edge case.
        bool intStart = false; // a stat for control 
        int start = 0, len = 0;
        unordered_map<string, bool> stat;
        for(int i=0; i<word.size(); i++) {
            if (!isNumber(word[i]) ) {
                if (intStart) {
                    while(word[start]=='0') {
                        start++, len--;
                    }
                    stat[word.substr(start, len)] = true;
                    intStart=false; 
                }
                continue;
            }
            
            if (intStart == false) {
                intStart = true;
                start = i;
                len = 1;
            }else {
                len++;
            }
        }
        return stat.size();           
    }
};