leetcode

Author: ayoubzulfiqar

FirstUniqueCharacterInAString/first_unique_character_in_a_string.dart

@@ -0,0 +1,93 @@
+/*
+
+-* 387. First Unique Character in a String *-
+
+Given a string s, find the first non-repeating character in it and return its index. If it does not exist, return -1.
+
+
+
+Example 1:
+
+Input: s = "leetcode"
+Output: 0
+Example 2:
+
+Input: s = "loveleetcode"
+Output: 2
+Example 3:
+
+Input: s = "aabb"
+Output: -1
+
+
+Constraints:
+
+1 <= s.length <= 105
+s consists of only lowercase English letters.
+
+
+
+
+
+
+
+*/
+
+import 'dart:collection';
+
+class Solution {
+  int firstUniqChar(String s) {
+    // hashmap to store the unique values
+    HashMap<String, int?> map = HashMap();
+    // looping through each and every element in the String
+    for (int i = 0; i < s.length; i++) {
+      // assigning the int as index for every element
+      map[s[i]] = (map[s[i]] ?? 0) + 1;
+    }
+    // looping again
+    for (int i = 0; i < s.length; i++) {
+      // if the element matches with index value as saved above
+      if (map[s[i]] == 1) {
+        // than we will return that element
+        return i;
+      }
+    }
+    // sentinel value
+    return -1;
+  }
+}
+
+class B {
+  int firstUniqChar(String s) {
+    // index as ans
+    int ans = 0;
+    // into array list of each and every character
+    List<String> chars = s.split("");
+    // if that character is inside the array of character
+    for (String char in chars) {
+      // comparing first to last index
+      if (s.indexOf(char) == s.lastIndexOf(char)) {
+        // assigning the index to our value
+        return ans = s.indexOf(char);
+      } else {
+        ans = -1;
+      }
+    }
+    return ans;
+  }
+}
+
+class C {
+  int firstUniqChar(String s) {
+    // frequency of array based on the length of alphabets inn ENGLISH
+    List<int> freq = List.filled(26, 0);
+    // looping through the length of string
+    for (int i = 0; i < s.length; i++)
+      // getting the index of the each individual string character
+      freq[s.codeUnitAt(i) - 'a'.codeUnitAt(0)]++;
+    for (int i = 0; i < s.length; i++)
+      // if it matches with index we will return
+      if (freq[s.codeUnitAt(i) - 'a'.codeUnitAt(0)] == 1) return i;
+    return -1;
+  }
+}

FirstUniqueCharacterInAString/first_unique_character_in_a_string.go

@@ -0,0 +1,30 @@
+package main
+
+func firstUniqChar(s string) int {
+	flags := make([]int, 26)
+	for i := range flags {
+		flags[i] = -1
+	}
+	slen := len(s)
+
+	for i, ch := range s {
+		idx := byte(ch - 'a')
+		if flags[idx] == -1 {
+			flags[idx] = i
+		} else {
+			flags[idx] = slen
+		}
+	}
+
+	min := slen
+	for i := range flags {
+		if flags[i] >= 0 && flags[i] < len(s) && flags[i] < min {
+			min = flags[i]
+		}
+	}
+
+	if min == slen {
+		return -1
+	}
+	return min
+}

FirstUniqueCharacterInAString/first_unique_character_in_a_string.md

@@ -0,0 +1,71 @@
+# 🔥 First Unique Character in a String 🔥 || 3 Approaches || Simple Fast and Easy || with Explanation
+
+## Solution - 1 HashMap
+
+```dart
+class Solution {
+  int firstUniqChar(String s) {
+    // hashmap to store the unique values
+    HashMap<String, int?> map = HashMap();
+    // looping through each and every element in the String
+    for (int i = 0; i < s.length; i++) {
+      // assigning the int as index for every element
+      map[s[i]] = (map[s[i]] ?? 0) + 1;
+    }
+    // looping again
+    for (int i = 0; i < s.length; i++) {
+      // if the element matches with index value as saved above
+      if (map[s[i]] == 1) {
+        // than we will return that element
+        return i;
+      }
+    }
+    // sentinel value
+    return -1;
+  }
+}
+```
+
+## Solution - 2 Frequency Array
+
+```dart
+class Solution {
+  int firstUniqChar(String s) {
+    // index as ans
+    int ans = 0;
+    // into array list of each and every character
+    List<String> chars = s.split("");
+    // if that character is inside the array of character
+    for (String char in chars) {
+      // comparing first to last index
+      if (s.indexOf(char) == s.lastIndexOf(char)) {
+        // assigning the index to our value
+        return ans = s.indexOf(char);
+      } else {
+        ans = -1;
+      }
+    }
+    return ans;
+  }
+}
+
+```
+
+## Solution - 3
+
+```dart
+class Solution {
+  int firstUniqChar(String s) {
+    // frequency of array based on the length of alphabets inn ENGLISH
+    List<int> freq = List.filled(26, 0);
+    // looping through the length of string
+    for (int i = 0; i < s.length; i++)
+      // getting the index of the each individual string character
+      freq[s.codeUnitAt(i) - 'a'.codeUnitAt(0)]++;
+    for (int i = 0; i < s.length; i++)
+      // if it matches with index we will return
+      if (freq[s.codeUnitAt(i) - 'a'.codeUnitAt(0)] == 1) return i;
+    return -1;
+  }
+}
+```

README.md

@@ -138,6 +138,7 @@ This repo contain leetcode solution using DART and GO programming language. Most
 - [**367.** Valid Perfect Square](ValidPerfectSquare/valid_perfect_square.dart)
 - [**383.** Ransom Note](RansomNote/ransom_note.dart)
 - [**587.** Erect the Fence](ErectTheFence/erect_the_fence.dart)
+- [**387.** First Unique Character in a String](FirstUniqueCharacterInAString/first_unique_character_in_a_string.dart)
 
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