[feat ]: leetcode 1137

Signed-off-by: Bo-Wei Chen(BWbwchen) <tim.chenbw@gmail.com>

Author: BWbwchen

leetcode/1137_N-th-Tribonacci-Number.cpp

@@ -0,0 +1,17 @@
+class Solution {
+public:
+    int tribonacci(int n) {
+        if (n == 0)
+            return 0;
+        else if (n < 3)
+            return 1;
+        vector<int> v(n+1, 0);
+        v[0] = 0;
+        v[1] = 1;
+        v[2] = 1;
+        for (int i = 3; i <= n; ++i) {
+            v[i] = v[i-1] + v[i-2] + v[i-3];
+        }
+        return v[n];
+    }
+};