feat: add LeetCode problem 100 - Same Tree

leetcode/src/100.c

@@ -0,0 +1,27 @@
+/**
+ * LeetCode Problem 100 - Same Tree
+ * Check if two binary trees are the same.
+ *
+ * Two binary trees are the same if they are structurally identical and the nodes have the same value.
+ */
+
+/**
+ * Definition for a binary tree node:
+ * struct TreeNode {
+ *     int val;
+ *     struct TreeNode *left;
+ *     struct TreeNode *right;
+ * };
+ */
+
+ bool isSameTree(struct TreeNode* p, struct TreeNode* q) {
+    if (p == NULL && q == NULL) {
+        return true;
+    }
+    if (p == NULL || q == NULL) {
+        return false;
+    }
+    return (p->val == q->val) &&
+           isSameTree(p->left, q->left) &&
+           isSameTree(p->right, q->right);
+}