<p>Given two non-negative integers, <code>num1</code> and <code>num2</code> represented as string, return <em>the sum of</em> <code>num1</code> <em>and</em> <code>num2</code> <em>as a string</em>.</p>

<p>You must solve the problem without using any built-in library for handling large integers (such as <code>BigInteger</code>). You must also not convert the inputs to integers directly.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> num1 = &quot;11&quot;, num2 = &quot;123&quot;
<strong>Output:</strong> &quot;134&quot;
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> num1 = &quot;456&quot;, num2 = &quot;77&quot;
<strong>Output:</strong> &quot;533&quot;
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> num1 = &quot;0&quot;, num2 = &quot;0&quot;
<strong>Output:</strong> &quot;0&quot;
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= num1.length, num2.length &lt;= 10<sup>4</sup></code></li>
	<li><code>num1</code> and <code>num2</code> consist of only digits.</li>
	<li><code>num1</code> and <code>num2</code> don&#39;t have any leading zeros except for the zero itself.</li>
</ul>

class Solution {
public:
    string func(string num1, string num2){
        int d = num1.size()-num2.size();
        string ans="";
        char carry='0';
        for(int i=0; i<d; i++)num2 = "0" + num2;
        for(int i=num1.size()-1; i>=0; i--){
            char temp =  '0' + ((((num1[i]-'0')+(num2[i]-'0')+(carry-'0')) % 10));
            ans = temp+ans;
            carry = '0' + (((num1[i]-'0')+(num2[i]-'0')+(carry-'0')) / 10);
            cout<<carry<<endl;
        }
        if(carry!='0')ans=carry+ans;
        return ans;
    }
    string addStrings(string num1, string num2) {
        if(num1.size()<num2.size())return func(num2, num1);
        return func(num1, num2);
    }
};
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