Solved problem 746 : Min Cost Climbing Stairs

Author: racoelhosilva

Dynamic Programming 1D/Easy/70_ClimbingStairs.cpp

@@ -2,7 +2,7 @@
  * Problem: 70 
  * Name: Climbing Stairs
  * Difficulty: Easy
- * Topic: Dynamic Programming (1D)
+ * Topic: Dynamic Programming 1D
  * Link: https://leetcode.com/problems/climbing-stairs/
  */
 

Dynamic Programming 1D/Easy/746_MinCostClimbingStairs.cpp

@@ -0,0 +1,49 @@
+/* 
+ * Problem: 746 
+ * Name: Min Cost Climbing Stairs
+ * Difficulty: Easy
+ * Topic: Dynamic Programming 1D
+ * Link: https://leetcode.com/problems/
+ */
+ 
+#include <bits/stdc++.h>
+using namespace std;
+
+//      Storing the minimum values for each of the steps
+// Time Complexity: O(n)
+// Space Complexity: O(n)
+int minCostClimbingStairsMemo(vector<int>& cost) {
+    if (cost.size() < 2) {return 0;}
+    vector<int> minStepCost(cost.size()+1, 0);
+    for (int step = 2; step <= cost.size(); step++){
+        minStepCost[step] = min(minStepCost[step-2] + cost[step-2], minStepCost[step-1] + cost[step-1]);
+    }
+    return minStepCost[cost.size()];
+}
+
+//      Storing the minimum values of the previous two steps
+// Time Complexity: O(n)
+// Space Complexity: O(1)
+int minCostClimbingStairsMemoPrevious(vector<int>& cost) {
+    if (cost.size() < 2) {return 0;}
+    vector<int> minStepCost(2, 0);
+    for (int step = 2; step <= cost.size(); step++){
+        minStepCost[step % 2] = min(minStepCost[(step-2) % 2] + cost[step-2], minStepCost[(step-1) % 2] + cost[step-1]);
+    }
+    return minStepCost[cost.size() % 2];
+}
+
+//      Fibonacci-like approach
+// Time Complexity: O(n)
+// Space Complexity: O(1)
+int minCostClimbingStairsFibonacci(vector<int>& cost) {
+    if (cost.size() < 2) {return 0;}
+    int twoStepBefore = cost[0];
+    int oneStepBefore = cost[1];
+    for (int step = 2; step < cost.size(); step++){
+        int current = cost[step] + min(oneStepBefore, twoStepBefore);
+        twoStepBefore = oneStepBefore;
+        oneStepBefore = current;
+    }
+    return min(oneStepBefore, twoStepBefore);
+}

README.md

@@ -16,7 +16,7 @@
 
 ### Problems Solved
 
-| Total | 45 |
+| Total | 46 |
 |:---:|:---:|
 
 #### Search By Topic
@@ -28,7 +28,7 @@
 | Binary Search | 2 |
 | Binary Trees | 9 |
 | Bit Manipulation | 6 |
-| Dynamic Programming 1D | 1 |
+| Dynamic Programming 1D | 2 |
 | Dynamic Programming 2D | 0 |
 | Graphs | 1 |
 | Graphs Advanced | 0 |
@@ -46,7 +46,7 @@
 
 | Difficulty | Number |
 |:---|---:|
-| Easy | 44 |
+| Easy | 45 |
 | Medium | 1 |
 | Hard | 0 |