Facebook phone interview tomorrow

Author: kaidul

Diff for: source-code/Best_Time_to_Buy_and_Sell_Stock_with_Transaction_Fee.cpp

@@ -0,0 +1,21 @@
+class Solution {
+public:
+    int maxProfit(vector<int>& prices, int fee) {
+        int n = (int)prices.size();
+        if(n == 0) return 0;
+        vector<int> buy(n), sell(n), hold(n), skip(n);
+        
+        buy[0] = -prices[0];
+        hold[0] = -prices[0];
+        sell[0] = skip[0] = 0;
+        
+        for(int i = 1; i < n; i++) {
+            buy[i] = max(skip[i - 1], sell[i - 1]) - prices[i];
+            skip[i] = max(skip[i - 1], sell[i - 1]);
+            hold[i] = max(hold[i - 1], buy[i - 1]);
+            sell[i] = max(hold[i - 1], buy[i - 1]) + prices[i] - fee;
+        }
+        
+        return max(buy[n - 1], max(skip[n - 1], max(hold[n - 1], sell[n - 1])));
+    }
+};

Diff for: source-code/Graph_Valid_Tree.cpp

@@ -1,18 +1,19 @@
 class Solution {
 public:
-    bool hasCycle(int parent, int node, vector<vector<int> >& adj, vector<bool>& visited) {
+    bool isTree(int parent, int node, vector<vector<int> >& adj, vector<bool>& visited) {
         visited[node] = true;
-        bool ret = true;
         for(int i = 0; i < (int) adj[node].size(); ++i) {
             if(adj[node][i] != parent) {
                 int child = adj[node][i];
                 if(visited[child]) {
                     return false;
                 }
-                ret &= hasCycle(node, child, adj, visited);
+                if(!isTree(node, child, adj, visited)) {
+                    return false;
+                }
             }
         }
-        return ret;
+        return true;
     }
 
     bool validTree(int n, vector<pair<int, int>>& edges) {
@@ -24,13 +25,13 @@ class Solution {
             adj[v].push_back(u);
         }
         vector<bool> visited(n, false);
-        bool isTree = hasCycle(-1, 0, adj, visited);
+        bool isValidTree = isTree(-1, 0, adj, visited);
 
-        if(isTree) for(int i = 0; i < n; ++i) {
+        if(isValidTree) for(int i = 0; i < n; ++i) {
             if(!visited[i]) {
                 return false;
             }
         }
-        return isTree;
+        return isValidTree;
     }
 };

Diff for: source-code/H-Index.cpp

@@ -5,8 +5,8 @@ class Solution {
         int hIndx = 0;
         for(int i = 0; i < citations.size(); ++i) {
             if(citations[i] < i + 1) break;
-            hIndx = max(hIndx, i + 1);
+            hIndx = i + 1;
         }
         return hIndx;
     }
-};
+};

Diff for: source-code/H-Indx_II.cpp renamed to source-code/H-Index_II.cpp

@@ -14,7 +14,7 @@ class Solution {
             if(citations[mid] < n - mid) {
                 left = mid + 1;
             } else {
-                hIndx = max(hIndx, n - mid);
+                hIndx = n - mid;
                 right = mid;
             }
         }
@@ -30,9 +30,9 @@ class Solution {
         int n = citations.size();
         for(int i = n - 1; i >= 0; --i) {
             if(citations[i] < n - i) break;
-            hIndx = max(hIndx, n - i);
+            hIndx = n - i;
         }
         return hIndx;
     }
 };
-*/
+*/

Diff for: source-code/Integer_to_English_Words.cpp

@@ -75,10 +75,6 @@ class Solution {
             process(r, result);
         }
 
-        if(result[(int)result.length() - 1] == ' ') {
-            result.erase((int)result.length() - 1, 1);
-        }
-        
-        return result;
+        return result.erase((int)result.length() - 1, 1);
     }
-};
+};