add queue and map solve

Author: colorbox

387/step2_2_suggested.cpp

@@ -0,0 +1,34 @@
+/*
+https://github.com/colorbox/leetcode/pull/29#discussion_r1861430039
+を見てそれを参考に自分で書いた解法、比較用
+*/
+class Solution {
+ public:
+  int firstUniqChar(string s) {
+    queue<CharacterAndCount> queue;
+    map<char, int> character_to_count;
+    for (int i = 0; i < s.size(); i++) {
+      char c = s[i];
+      character_to_count[c]++;
+      queue.push({c, i});
+      while (true) {
+        char front_character = queue.front().character;
+        if (character_to_count[front_character] > 1) {
+          queue.pop();
+        } else {
+          break;
+        }
+      }
+    }
+    if (queue.empty()) {
+      return -1;
+    }
+    return queue.front().index;
+  }
+
+ private:
+  struct CharacterAndCount {
+    char character;
+    int index;
+  };
+};

387/step2_2_suggested_fixed.cpp

@@ -0,0 +1,31 @@
+/*
+step2_2_suggested.cpp
+を
+https://github.com/colorbox/leetcode/pull/29#discussion_r1861430039
+の書き方に沿って修正したコード、参照用
+*/
+class Solution {
+ public:
+  int firstUniqChar(string s) {
+    queue<CharacterAndCount> characters;
+    map<char, int> character_to_count;
+    for (int i = 0; i < s.size(); ++i) {
+      char c = s[i];
+      ++character_to_count[c];
+      characters.push({c, i});
+      while (character_to_count[characters.front().character] >= 2) {
+        characters.pop();
+      }
+    }
+    if (characters.empty()) {
+      return -1;
+    }
+    return characters.front().index;
+  }
+
+ private:
+  struct CharacterAndCount {
+    char character;
+    int index;
+  };
+};