n-th-tribonacci-number

malipramod · malipramod · commit 57ea7f1c5303 · 2019-07-28T10:07:31.000+05:30
diff --git a/easy/1137 n-th-tribonacci-number/n-th-tribonacci-number.js b/easy/1137 n-th-tribonacci-number/n-th-tribonacci-number.js
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+/**
+ * @param {number} n
+ * @return {number}
+ */
+var tribonacci = function (n) {
+    let first = 0, second = 0, third = 1;
+    let result = 0;
+    n = n+1;
+    if (n == 0) return first;
+    if (n == 1) return second;
+    if (n == 2) return third;
+
+    while (n > 2) {
+        result = first + second + third;
+        first = second;
+        second = third;
+        third = result;
+        n--;
+    }
+    return result;
+};
+
+console.log(tribonacci(3))
diff --git a/easy/1137 n-th-tribonacci-number/readme.md b/easy/1137 n-th-tribonacci-number/readme.md
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+# 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.'
