0067. Add Binary

Author: coderbean

markdown/0067. Add Binary.md

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+### [67\. Add Binary](https://leetcode.com/problems/add-binary/)
+
+Difficulty: **Easy**
+
+
+Given two binary strings, return their sum (also a binary string).
+
+The input strings are both **non-empty** and contains only characters `1` or `0`.
+
+**Example 1:**
+
+```
+Input: a = "11", b = "1"
+Output: "100"
+```
+
+**Example 2:**
+
+```
+Input: a = "1010", b = "1011"
+Output: "10101"
+```
+
+
+#### Solution
+
+Language: **Java**
+
+```java
+class Solution {
+    public String addBinary(String a, String b) {
+        char[] shortStr;
+        char[] longStr;
+        if (a.length() > b.length()) {
+            shortStr = b.toCharArray();
+            longStr = a.toCharArray();
+        } else {
+            shortStr = a.toCharArray();
+            longStr = b.toCharArray();
+        }
+        int plusNum = 0;
+        int i = longStr.length - 1;
+        int j = shortStr.length - 1;
+        do {
+            int sum = longStr[i] - '0' + plusNum;
+            if (j >= 0) {
+                sum += (shortStr[j] - '0');
+            }
+            longStr[i] = (char) (sum % 2 + '0');
+            plusNum = sum / 2;
+            i--;
+            j--;
+        } while (i >= 0);
+        if (plusNum > 0) {
+            return "1" + String.valueOf(longStr);
+        } else {
+            return String.valueOf(longStr);
+        }
+    }
+}
+```
+![](https://raw.githubusercontent.com/PicGoBed/PicBed/master/20190719175928.png)

src/main/java/leetcode/_67_/Main.java

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+package leetcode._67_;
+
+/**
+ * Created by zhangbo54 on 2019-03-04.
+ */
+public class Main {
+    public static void main(String[] args) {
+        Solution solution = new Solution();
+        System.out.println(solution.addBinary("1010", "1011"));
+        System.out.println(solution.addBinary("11", "1"));
+        System.out.println(solution.addBinary("10100000100100110110010000010101111011011001101110111111111101000000101111001110001111100001101", "110101001011101110001111100110001010100001101011101010000011011011001011101111001100000011011110011"));
+    }
+}

src/main/java/leetcode/_67_/Solution.java

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+package leetcode._67_;
+
+class Solution {
+    public String addBinary(String a, String b) {
+        char[] shortStr;
+        char[] longStr;
+        if (a.length() > b.length()) {
+            shortStr = b.toCharArray();
+            longStr = a.toCharArray();
+        } else {
+            shortStr = a.toCharArray();
+            longStr = b.toCharArray();
+        }
+        int plusNum = 0;
+        int i = longStr.length - 1;
+        int j = shortStr.length - 1;
+        do {
+            int sum = longStr[i] - '0' + plusNum;
+            if (j >= 0) {
+                sum += (shortStr[j] - '0');
+            }
+            longStr[i] = (char) (sum % 2 + '0');
+            plusNum = sum / 2;
+            i--;
+            j--;
+        } while (i >= 0);
+        if (plusNum > 0) {
+            return "1" + String.valueOf(longStr);
+        } else {
+            return String.valueOf(longStr);
+        }
+    }
+}

src/main/java/leetcode/_67_/solution.md

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+### [67\. Add Binary](https://leetcode.com/problems/add-binary/)
+
+Difficulty: **Easy**
+
+
+Given two binary strings, return their sum (also a binary string).
+
+The input strings are both **non-empty** and contains only characters `1` or `0`.
+
+**Example 1:**
+
+```
+Input: a = "11", b = "1"
+Output: "100"
+```
+
+**Example 2:**
+
+```
+Input: a = "1010", b = "1011"
+Output: "10101"
+```
+
+
+#### Solution
+
+Language: **Java**
+
+```java
+class Solution {
+    public String addBinary(String a, String b) {
+        char[] shortStr;
+        char[] longStr;
+        if (a.length() > b.length()) {
+            shortStr = b.toCharArray();
+            longStr = a.toCharArray();
+        } else {
+            shortStr = a.toCharArray();
+            longStr = b.toCharArray();
+        }
+        int plusNum = 0;
+        int i = longStr.length - 1;
+        int j = shortStr.length - 1;
+        do {
+            int sum = longStr[i] - '0' + plusNum;
+            if (j >= 0) {
+                sum += (shortStr[j] - '0');
+            }
+            longStr[i] = (char) (sum % 2 + '0');
+            plusNum = sum / 2;
+            i--;
+            j--;
+        } while (i >= 0);
+        if (plusNum > 0) {
+            return "1" + String.valueOf(longStr);
+        } else {
+            return String.valueOf(longStr);
+        }
+    }
+}
+```
+![](https://raw.githubusercontent.com/PicGoBed/PicBed/master/20190719175928.png)