3 files changed, 77 insertions, 0 deletions

diff --git a/top-interview-questions/easy/strings/03_first_unique_character.cc b/top-interview-questions/easy/strings/03_first_unique_character.cc
new file mode 100644
index 0000000..871f761
--- /dev/null
+++ b/top-interview-questions/easy/strings/03_first_unique_character.cc
@@ -0,0 +1,18 @@
+class Solution {
+public:
+    int firstUniqChar(string s) {
+        int count[256] = {};
+
+        for (char c : s) {
+            count[c]++;
+        }
+
+        for (size_t i = 0; i < s.size(); ++i) {
+            if (count[s[i]] == 1) {
+                return i;
+            }
+        }
+
+        return -1;
+    }
+};
diff --git a/top-interview-questions/easy/strings/04_valid_anagram.cc b/top-interview-questions/easy/strings/04_valid_anagram.cc
new file mode 100644
index 0000000..3ca6b7c
--- /dev/null
+++ b/top-interview-questions/easy/strings/04_valid_anagram.cc
@@ -0,0 +1,29 @@
+class Solution {
+public:
+    static void count(const string& s, int* counts) {
+        for (char c : s) {
+            counts[c]++;
+        }
+    }
+
+    bool isAnagram(string s, string t) {
+        if (s.size() != t.size()) {
+            return false;
+        }
+        // strings are equal length
+
+        int sCount[256] = {};
+        int tCount[256] = {};
+
+        count(s, sCount);
+        count(t, tCount);
+
+        for (char c : s) {
+            if (sCount[c] != tCount[c]) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+};
diff --git a/top-interview-questions/easy/strings/05_valid_palindrome.cc b/top-interview-questions/easy/strings/05_valid_palindrome.cc
new file mode 100644
index 0000000..1b4ca6f
--- /dev/null
+++ b/top-interview-questions/easy/strings/05_valid_palindrome.cc
@@ -0,0 +1,30 @@
+class Solution {
+public:
+    bool IsAlphaNum(char c) {
+        return
+            (('a' <= c) && (c <= 'z')) ||
+            (('A' <= c) && (c <= 'Z')) ||
+            (('0' <= c) && (c <= '9'));
+    }
+
+    void Transform(string& s) {
+        size_t j = 0;
+        for (size_t i = 0; i < s.size(); ++i) {
+            if (IsAlphaNum(s[i])) {
+                s[j] = std::tolower(s[i]);
+                j++;
+            }
+        }
+        s.resize(j);
+    }
+
+    bool isPalindrome(string s) {
+        Transform(s);
+        for (size_t i = 0; i < s.size()/2; ++i) {
+            if (s[i] != s[s.size()-i-1]) {
+                return false;
+            }
+        }
+        return true;
+    }
+};