dart solution

Author: bansalgaurav852

dart/0002-add-two-numbers.dart

@@ -0,0 +1,44 @@
+/**
+ * Definition for singly-linked list.
+ * class ListNode {
+ *   int val;
+ *   ListNode? next;
+ *   ListNode([this.val = 0, this.next]);
+ * }
+ */
+class Solution {
+  ListNode? addTwoNumbers(ListNode? l1, ListNode? l2) {
+    ListNode ?listnode ;
+    int carry = 0;
+    while (l1 != null || l2 != null) {
+        int val =(l1?.val ?? 0) + (l2?.val ?? 0)+carry;
+        l1=l1?.next;
+        l2=l2?.next;
+        if(val>9){
+            val=val-10;
+            carry=1;
+        }else{
+            carry = 0;
+        }
+
+      
+     print("val $val");
+
+      if(listnode!=null)
+        listnode = ListNode(val,listnode);
+
+    else
+     listnode = ListNode(val);
+    }
+    if(carry!=0){
+        listnode = ListNode(carry,listnode);
+    }
+    var list ;
+    while(listnode!=null){
+        list = ListNode(listnode.val,list);;
+        listnode = listnode?.next;
+    }
+      return list;
+  }
+
+}

dart/0003-longest-substring-without-repeating-characters.dart

@@ -0,0 +1,27 @@
+class Solution {
+  int lengthOfLongestSubstring(String s) {
+    int max = 0;
+    Map<String, int> map = {};
+
+    List<String> list = s.split('');
+    List<String> result = [];
+
+    for (int i = 0; i < list.length; i++) {
+      if (!result.contains(list[i])) {
+        result.add(list[i]);
+      } else {
+        map.putIfAbsent(result.join(), () => result.length);
+        while (result.contains(list[i])) {
+          result.removeAt(0);
+        }
+        result.add(list[i]);
+      }
+    }
+
+    map.putIfAbsent(result.join(), () => result.length);
+    map.forEach((key, value) {
+      max = max > value ? max : value;
+    });
+    return max;
+  }
+}

dart/0028-find-the-index-of-the-first-occurrence-in-a-string.dart

@@ -0,0 +1,6 @@
+class Solution {
+  int strStr(String haystack, String needle) {
+    var result = haystack.replaceAll(needle, '0').indexOf('0');
+    return result;
+  }
+}