Time: 5 ms (42.73%), Space: 6 MB (17.60%) - LeetHub

Author: Inventor77

509-fibonacci-number/509-fibonacci-number.cpp

@@ -1,11 +1,13 @@
 class Solution {
 public:
-    int rec(int i) {
+    int rec(int i, vector<int> &dp) {
         if(i <= 1) return i;
-        return rec(i - 1) + rec(i - 2);
+        if(dp[i] != -1) return dp[i];
+        return dp[i] = rec(i - 1, dp) + rec(i - 2, dp);
     }
 
     int fib(int n) {
-        return rec(n);
+        vector<int> v(n + 1, -1);
+        return rec(n, v);
     }
 };