DP on Mar 11

Author: AnandrewChan

DP/70.climbing-stairs.cpp

@@ -43,7 +43,16 @@
 class Solution {
 public:
     int climbStairs(int n) {
-        
+        if(n==0)return 0;
+        if(n==1)return 1;
+        if(n==2)return 2;
+        int a=1,b=2;
+        for(int i=2;i<n;i++){
+            int tmp=a+b;
+            a=b;
+            b=tmp;
+        }
+        return b;
     }
 };
 

DP/746.min-cost-climbing-stairs.cpp

@@ -0,0 +1,65 @@
+/*
+ * @lc app=leetcode id=746 lang=cpp
+ *
+ * [746] Min Cost Climbing Stairs
+ *
+ * https://leetcode.com/problems/min-cost-climbing-stairs/description/
+ *
+ * algorithms
+ * Easy (46.04%)
+ * Total Accepted:    68.1K
+ * Total Submissions: 147.6K
+ * Testcase Example:  '[0,0,0,0]'
+ *
+ * 
+ * On a staircase, the i-th step has some non-negative cost cost[i] assigned (0
+ * indexed).
+ * 
+ * Once you pay the cost, you can either climb one or two steps. You need to
+ * find minimum cost to reach the top of the floor, and you can either start
+ * from the step with index 0, or the step with index 1.
+ * 
+ * 
+ * Example 1:
+ * 
+ * Input: cost = [10, 15, 20]
+ * Output: 15
+ * Explanation: Cheapest is start on cost[1], pay that cost and go to the
+ * top.
+ * 
+ * 
+ * 
+ * Example 2:
+ * 
+ * Input: cost = [1, 100, 1, 1, 1, 100, 1, 1, 100, 1]
+ * Output: 6
+ * Explanation: Cheapest is start on cost[0], and only step on 1s, skipping
+ * cost[3].
+ * 
+ * 
+ * 
+ * Note:
+ * 
+ * cost will have a length in the range [2, 1000].
+ * Every cost[i] will be an integer in the range [0, 999].
+ * 
+ * 
+ */
+class Solution
+{
+  public:
+    int minCostClimbingStairs(vector<int> &cost)
+    {
+        int s = cost.size();
+        if (s == 0)
+            return 0;
+        if (s == 1)
+            return cost[0];
+        int a[] = {cost[0], cost[1]};
+        for (int i = 2; i < s; i++)
+        {
+            a[i % 2] = min(cost[i] + a[0], cost[i] + a[1]);
+        }
+        return min(a[0], a[1]);
+    }
+};