leetcode

Author: ayoubzulfiqar

.gitignore

@@ -0,0 +1,76 @@
+/*
+
+
+
+
+-* 1137. N-th Tribonacci Number *-
+
+
+
+The Tribonacci sequence Tn is defined as follows: 
+
+T0 = 0, T1 = 1, T2 = 1, and Tn+3 = Tn + Tn+1 + Tn+2 for n >= 0.
+
+Given n, return the value of Tn.
+
+ 
+
+Example 1:
+
+Input: n = 4
+Output: 4
+Explanation:
+T_3 = 0 + 1 + 1 = 2
+T_4 = 1 + 1 + 2 = 4
+Example 2:
+
+Input: n = 25
+Output: 1389537
+ 
+
+Constraints:
+
+0 <= n <= 37
+The answer is guaranteed to fit within a 32-bit integer, ie. answer <= 2^31 - 1.
+
+
+*/
+
+class Solution {
+  int tribonacci(int n) {
+    if (n == 0) return 0;
+    if (n == 1 || n == 2) return 1;
+    List<int> Tribonacci = List.filled(n + 1, 0);
+    Tribonacci[0] = 0;
+    Tribonacci[1] = 1;
+    Tribonacci[2] = 1;
+    for (int i = 3; i < n + 1; i++) {
+      Tribonacci[i] = Tribonacci[i - 1] + Tribonacci[i - 2] + Tribonacci[i - 3];
+    }
+    return Tribonacci[n];
+  }
+}
+
+class B {
+  int tribonacci(int n) {
+    if (n == 0) return 0;
+    if (n == 1) return 1;
+    if (n == 2) return 1;
+    int a = 0, b = 1, c = 1, d = 0;
+    for (int i = 3; i <= n; i++) {
+      d = a + b + c;
+      a = b;
+      b = c;
+      c = d;
+    }
+    return d;
+  }
+}
+
+class C {
+  int tribonacci(int n) {
+    if (n < 2) return n;
+    if (n == 2) return 1;
+    return tribonacci(n - 1) + tribonacci(n - 2) + tribonacci(n - 3);
+  }
+}

N-thTribonacciNumber/n_th_tribonacci_number.dart

@@ -0,0 +1,49 @@
+package main
+
+// func tribonacci(n int) int {
+// 	if n == 0 {
+// 		return 0
+// 	}
+// 	if n == 1 || n == 2 {
+// 		return 1
+// 	}
+// 	var Tribonacci []int = make([]int, n+1)
+// 	Tribonacci[0] = 0
+// 	Tribonacci[1] = 1
+// 	Tribonacci[2] = 1
+// 	for i := 3; i < n+1; i++ {
+// 		Tribonacci[i] = Tribonacci[i-1] + Tribonacci[i-2] + Tribonacci[i-3]
+// 	}
+// 	return Tribonacci[n]
+// }
+
+// func tribonacci(n int) int {
+// if n == 0 {
+// 	return 0
+// }
+// if n == 1 || n == 2 {
+// 	return 1
+// }
+
+// 	var a int = 0
+// 	var b int = 1
+// 	var c int = 1
+// 	var d int = 0
+// 	for i := 3; i <= n; i++ {
+// 		d = a + b + c
+// 		a = b
+// 		b = c
+// 		c = d
+// 	}
+// 	return d
+// }
+
+func tribonacci(n int) int {
+	if n == 0 {
+		return 0
+	}
+	if n == 1 || n == 2 {
+		return 1
+	}
+	return tribonacci(n-1) + tribonacci(n-2) + tribonacci(n-3)
+}

N-thTribonacciNumber/n_th_tribonacci_number.go

@@ -0,0 +1,71 @@
+# 🔥 3 Approaches 🔥 || Simple Fast and Easy || with Explanation
+
+## Solution
+
+### Intuition of this Problem
+
+T[n] = T[n-1] + T[n-2] + T[n-3]
+
+NOTE - PLEASE READ APPROACH FIRST THEN SEE THE CODE. YOU WILL DEFINITELY UNDERSTAND THE CODE LINE BY LINE AFTER SEEING THE APPROACH.
+
+### Approach for this Problem
+
+1. Initialize a vector "Tribonacci" with n+1 elements
+2. Check if n is 0, if true return 0
+3. Check if n is 1, if true return 1
+4. Check if n is 2, if true return 1
+5. Set Tribonacci[0] = 0, Tribonacci[1] = 1, Tribonacci[2] = 1
+6. Iterate from i = 3 to n+1
+7. Set Tribonacci[i] = Tribonacci[i-1] + Tribonacci[i-2] + Tribonacci[i-3]
+8. Return Tribonacci[n]
+
+### Code - Memoization
+
+```dart
+class Solution {
+  int tribonacci(int n) {
+    if (n == 0) return 0;
+    if (n == 1 || n == 2) return 1;
+    List<int> Tribonacci = List.filled(n + 1, 0);
+    Tribonacci[0] = 0;
+    Tribonacci[1] = 1;
+    Tribonacci[2] = 1;
+    for (int i = 3; i < n + 1; i++) {
+      Tribonacci[i] = Tribonacci[i - 1] + Tribonacci[i - 2] + Tribonacci[i - 3];
+    }
+    return Tribonacci[n];
+  }
+}
+```
+
+### Code - Iterative
+
+```dart
+class Solution {
+  int tribonacci(int n) {
+    if (n == 0) return 0;
+    if (n == 1) return 1;
+    if (n == 2) return 1;
+    int a = 0, b = 1, c = 1, d = 0;
+    for (int i = 3; i <= n; i++) {
+      d = a + b + c;
+      a = b;
+      b = c;
+      c = d;
+    }
+    return d;
+  }
+}
+```
+
+### Code - Recursive
+
+```dart
+class Solution {
+  int tribonacci(int n) {
+    if (n < 2) return n;
+    if (n == 2) return 1;
+    return tribonacci(n - 1) + tribonacci(n - 2) + tribonacci(n - 3);
+  }
+}
+```

N-thTribonacciNumber/n_th_tribonacci_number.md

@@ -198,6 +198,7 @@ This repo contain leetcode solution using DART and GO programming language. Most
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+- [**1137.** N-th Tribonacci Number](N-thTribonacciNumber/n_th_tribonacci_number.dart)
 
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