solutions: 1137 - N-th Tribonacci Number (Easy)

- reformat solution 1 code

solutions/1100-1199/1137-n-th-tribonacci-number-easy.md

@@ -50,19 +50,19 @@ Output: 1389537
 // SC: O(N)
 class Solution {
 public:
-	// since first three numbers are given, 
-	// let dp[i] be the value of T_n
-	// we can build the dp[i] based on dp[i - 1] + dp[i - 2] + dp[i - 3]
+    // since first three numbers are given,
+    // let dp[i] be the value of T_n
+    // we can build the dp[i] based on dp[i - 1] + dp[i - 2] + dp[i - 3]
     int tribonacci(int n) {
-	    // first three numbers are known
+        // first three numbers are known
         if (n == 0) return 0;
         if (n == 1 || n == 2) return 1;
-		// dp[i]: the value of T_n
+        // dp[i]: the value of T_n
         vector<int> dp(n + 1);
-		// base case
+        // base case
         dp[0] = 0;
         dp[1] = dp[2] = 1;
-		// dp[i] is the sum of the previous three values
+        // dp[i] is the sum of the previous three values
         for(int i = 3; i <= n; i++) dp[i] = dp[i - 1] + dp[i - 2] + dp[i - 3];
         return dp[n];
     }