add maxProfit.cpp

Author: kamyu104

C++/maxProfitI.cpp

@@ -0,0 +1,21 @@
+// Time Complexity: O(n)
+// Space Complexity: O(1)
+
+class Solution {
+    public:
+        int maxProfit(vector<int> &prices) {
+            const int n = prices.size();
+
+            if(n < 2)
+                return 0;
+
+            // Greedy Algorithm
+            int ans = 0;
+            for(int i = 1, valley = prices[0]; i < n; ++i) {
+                ans = max(ans, prices[i] - valley);
+                valley = min(valley, prices[i]);
+            }
+
+            return ans;
+        }
+};

C++/maxProfitII.cpp

@@ -0,0 +1,18 @@
+// Time Complexity: O(n)
+// Space Complexity: O(1)
+
+class Solution {
+    public:
+        int maxProfit(vector<int> &prices) {
+            const int n = prices.size();
+            int ans = 0;
+
+            for(int i = 1; i < n; ++i) {
+                int diff = prices[i] - prices[i - 1];
+                if(diff > 0)
+                    ans += diff;
+            }
+
+            return ans;
+        }
+};

C++/maxProfitIII.cpp

@@ -0,0 +1,32 @@
+// Time Complexity: O(n)
+// Space Complexity: O(n)
+
+class Solution {
+    public:
+        int maxProfit(vector<int> &prices) {
+            const int n = prices.size();
+
+            if(n < 2)
+                return 0;
+
+            vector<int> f(n, 0);
+            vector<int> g(n, 0);
+
+            for(int i = 1, valley = prices[0]; i < n; ++i) {
+                f[i] = max(f[i - 1], prices[i] - valley);
+                valley = min(valley, prices[i]);
+            }
+
+            for(int i = n - 2, peak = prices[n - 1]; i >= 0; --i) {
+                g[i] = max(g[i + 1], peak - prices[i]);
+                peak = max(peak, prices[i]);
+            }
+
+            int ans = 0;
+            for(int i = 0; i < n; ++i) {
+                ans = max(ans, f[i] + g[i]);
+            }
+
+            return ans;
+        }
+};