Add Strings

fishercoder1534 · fishercoder1534 · commit 45ce5d83b5b8 · 2016-10-09T09:49:13.000-07:00
diff --git a/EASY/src/easy/AddStrings.java b/EASY/src/easy/AddStrings.java
@@ -0,0 +1,40 @@
+package easy;
+
+/**
+ * Created by fishercoder1534 on 10/9/16.
+ */
+public class AddStrings {
+
+    public static String addStrings(String num1, String num2) {
+        if(num1 == null || num1.length() == 0) return num2;
+        else if(num2 == null || num2.length() == 0) return num1;
+
+        int i = num1.length()-1, j = num2.length()-1;
+        long carry = 0, sum = 0;
+        StringBuilder sb = new StringBuilder();
+        char[] char1 = num1.toCharArray();
+        char[] char2 = num2.toCharArray();
+        while(i >= 0  || j >= 0){
+            sum = carry;
+            if(i >= 0) sum += Character.getNumericValue(char1[i--]);
+            if(j >= 0) sum += Character.getNumericValue(char2[j--]);
+            carry = sum/10;
+            sb.append(sum%10);
+        }
+        if(carry != 0) sb.append(carry);
+
+        return sb.reverse().toString();
+    }
+
+    public static void main(String...args){
+//        String num1 = "123";
+//        String num2 = "34567";
+
+//        String num1 = "1";
+//        String num2 = "9";
+
+        String num1 = "9";
+        String num2 = "99";
+        System.out.println(addStrings(num1, num2));
+    }
+}
diff --git a/README.md b/README.md
@@ -1,6 +1,7 @@
 # fishercoderLeetcode
 |  #  |      Title               |         Solutions   | Time  | Space  | Difficulty | Tag | Notes
 |-----|--------------------------|---------------------|-------|--------|------------|-----|------
+|415|[Add Strings](https://leetcode.com/problems/add-strings/)|[Solution](../../blob/master/EASY/src/easy/AddStrings.java)| O(n)|O(1) | Easy|
 |350|[Intersection of Two Arrays II](https://leetcode.com/problems/intersection-of-two-arrays-ii/)|[Solution](../../blob/master/EASY/src/easy/IntersectionOfTwoArraysII.java)| O(m+n)|O((m+n)) could be optimized | Easy| HashMap, Binary Search
 |349|[Intersection of Two Arrays](https://leetcode.com/problems/intersection-of-two-arrays/)|[Solution](../../blob/master/EASY/src/easy/IntersectionOfTwoArrays.java)| O(m+n)|O(min(m,n)) | Easy| Two Pointers, Binary Search
 |325|[Maximum Size Subarray Sum Equals k](https://leetcode.com/problems/maximum-size-subarray-sum-equals-k/)|[Solution] | O(n)|O(n) | Medium| HashMap
