Create 04 - Space Optimized | DP | Approach.cpp

Author: JawadSher

24 - Dynamic Programming Problems/03 - Climbing Stairs/04 - Space Optimized | DP | Approach.cpp

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+class Solution {
+public:
+    // Function to calculate the number of ways to climb `n` stairs using optimized space
+    int climbStairs(int n) {
+        // Base cases: there's one way to stay at the 0th step (prev1) and one way to reach the 1st step (prev2)
+        int prev1 = 1;  // Represents the number of ways to reach the step (i-1)
+        int prev2 = 1;  // Represents the number of ways to reach the step (i-2)
+
+        // Iterate from step 2 to step n, calculating the number of ways to reach each step
+        for(int i = 2; i <= n; i++) {
+            // The number of ways to reach step i is the sum of the ways to reach step (i-1) and step (i-2)
+            int curr = prev1 + prev2;
+
+            // Update prev2 to prev1 (step (i-2) becomes the previous step)
+            prev2 = prev1;
+
+            // Update prev1 to curr (step (i-1) becomes the current step)
+            prev1 = curr;
+        }
+
+        // Return the number of ways to reach the nth step
+        return prev1;
+    }
+};