vault backup: 2022-09-05 17:13:55

OJ notes/pages/Leetcode Add-Strings.md

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+# Leetcode Add-Strings
+
+2022-09-05 17:07
+
+> ##### Data structures:
+>
+> #DS #string 
+>
+> ##### Difficulty:
+>
+> #coding_problem #difficulty-easy
+>
+> ##### Additional tags:
+>
+> #leetcode 
+>
+> ##### Revisions:
+>
+> N/A
+
+##### Links:
+
+- [Link to problem](https://leetcode.com/problems/add-strings/)
+
+---
+
+### Problem
+
+Given two non-negative integers, `num1` and `num2` represented as string, return _the sum of_ `num1` _and_ `num2` _as a string_.
+
+You must solve the problem without using any built-in library for handling large integers (such as `BigInteger`). You must also not convert the inputs to integers directly.
+
+#### Examples
+
+**Example 1:**
+
+**Input:** num1 = "11", num2 = "123"
+**Output:** "134"
+
+**Example 2:**
+
+**Input:** num1 = "456", num2 = "77"
+**Output:** "533"
+
+**Example 3:**
+
+**Input:** num1 = "0", num2 = "0"
+**Output:** "0"
+
+#### Constraints
+
+-   `1 <= num1.length, num2.length <= 104`
+-   `num1` and `num2` consist of only digits.
+-   `num1` and `num2` don't have any leading zeros except for the zero itself.
+
+### Thoughts
+
+> [!summary]
+> This is a #string operation problem
+
+Straightforward, just think how to calculate IRL.
+
+#TODO: try out faster solutions in discussion
+
+### Solution
+
+```cpp
+class Solution {
+public:
+  string addStrings(string num1, string num2) {
+    string ans = "";
+    int sum = 0;
+
+    while (!num1.empty() || !num2.empty() || sum != 0) {
+      if (!num1.empty()) {
+        sum += num1.back() - '0';
+        num1.pop_back();
+      }
+      if (!num2.empty()) {
+        sum += num2.back() - '0';
+        num2.pop_back();
+      }
+      ans.insert(0, 1, (sum % 10) + '0');
+      sum = sum / 10;
+    }
+
+    return ans;
+  }
+};
+```