Merge pull request neetcode-gh#1547 from MHamiid/patch-13

Create 297-Serialize-and-Deserialize-Binary-Tree.c

c/297-Serialize-and-Deserialize-Binary-Tree.c

@@ -0,0 +1,88 @@
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ * int val;
+ * struct TreeNode *left;
+ * struct TreeNode *right;
+ * };
+ */
+#define DATA_ALLOCATION_SIZE 10000
+
+typedef struct TreeNode TreeNode;
+
+void dfs_encode(TreeNode* node, char** data, int* dataIndex, int* dataSize)
+{
+ // Check if new space reallocation is needed
+ if((*dataIndex) + 10 >= *dataSize) // (+10) to add a little bit of margin for any data to be written in this function scope
+ {
+ // Reallocate data string for a bigger space
+ *dataSize += DATA_ALLOCATION_SIZE;
+ *data = (char*)realloc(*data, *dataSize * sizeof(char));
+ }
+
+ if(!node)
+ {
+ (*data)[(*dataIndex)++] = 'N';
+ (*data)[(*dataIndex)++] = ',';
+ return;
+ }
+
+ // Returns total number of characters written is returned excluding the null-character 
+ int charsWritten = sprintf(*data + *dataIndex, "%d", node->val);
+ *dataIndex += charsWritten;
+ (*data)[(*dataIndex)++] = ','; // This is actually is written in-place of the null terminator
+
+ dfs_encode(node->left, data, dataIndex, dataSize);
+ dfs_encode(node->right, data, dataIndex, dataSize);
+}
+
+TreeNode* dfs_decode(char** data)
+{
+ // Reached end of the string
+ if((*data)[0] == '\0')
+ {
+ return NULL;
+ }
+ else if((*data)[0] == 'N')
+ {
+ // Skip two chars ('N' and ',')
+ *data += 2;
+ return NULL;
+ }
+
+ TreeNode* node = (TreeNode*)malloc(sizeof(TreeNode));
+ char* endPtr = NULL; // Points to the first char after the numeric value
+
+ // Set the node value
+ node->val = strtol(*data, &endPtr, 10);
+ *data = endPtr + 1; // (+1) to skip the ','
+
+ node->left = dfs_decode(data);
+ node->right = dfs_decode(data);
+
+ return node;
+}
+
+/** Encodes a tree to a single string. */
+char* serialize(struct TreeNode* root) {
+ // Allocate the maximum possible number of nodes
+ int dataSize = DATA_ALLOCATION_SIZE;
+ char* data = (char*)malloc(dataSize * sizeof(char));
+ int dataIndex = 0; // points to the first empty space in the data string
+
+ dfs_encode(root, &data, &dataIndex, &dataSize);
+ // Add the null terminator
+ data[dataIndex] = '\0';
+
+ return data;
+}
+
+/** Decodes your encoded data to tree. */
+struct TreeNode* deserialize(char* data) {
+
+ return dfs_decode(&data);
+}
+
+// Your functions will be called as such:
+// char* data = serialize(root);
+// deserialize(data);