fixed the algorithm bug

Author: haoel

algorithms/cpp/minCostClimbingStairs/MinCostClimbingStairs.cpp

@@ -29,17 +29,29 @@
  * Every cost[i] will be an integer in the range [0, 999].
  * 
  ******************************************************************************************************/
-
 class Solution {
-public:
-    int minCostClimbingStairs(vector<int>& cost) {
-        vector<int> dp(cost.size() , 0);
-        dp[0] = cost[0];
-
-        for (int i=1; i<cost.size(); i++) {
-            dp[i] = min( cost[i] + dp[i-1], cost[i] + dp[i-2] );
+    public:
+        int minCostClimbingStairs(vector<int>& cost) {
+            return minCostClimbingStairs02(cost); 
+            return minCostClimbingStairs01(cost); 
+        }
+        int minCostClimbingStairs01(vector<int>& cost) {
+            vector<int> dp(cost.size() , 0);
+            dp[0] = cost[0];
+            dp[1] = cost[1];
+            for (int i=2; i<cost.size(); i++) {
+                dp[i] = min( dp[i-1], dp[i-2] ) + cost[i];
+            }
+            return min(dp[dp.size()-1], dp[dp.size()-2]);
         }
 
-        return min( dp[dp.size()-1], dp[dp.size()-2]);
-    }
+        int minCostClimbingStairs02(vector<int>& cost) {
+            int dp1 = cost[0], dp2 = cost[1];
+            for (int i=2; i<cost.size(); i++) {
+                int dp = min( dp1, dp2 ) + cost[i];
+                dp1 = dp2;
+                dp2 = dp;
+            }
+            return min (dp1, dp2);
+        }
 };