[CPP] 121. Best Time to Buy and Sell Stock

Author: UnresolvedCold

cpp/121-Best-Time-to-Buy-and-Sell-Stock.cpp

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+class Solution {
+public:
+    int maxProfit(vector<int>& prices) {
+        int n = prices.size();
+        // Preprocessing
+        // Polulate a smallest from beginning array
+        // Polulate a largest from the end array
+        vector<int> smallest(n, -1), largest(n, -1);
+        
+        smallest[0] = prices[0];
+        largest[n-1] = prices[n-1];
+        
+        for (int i = 1; i < n; i++) {
+            smallest[i] = min(smallest[i-1], prices[i]);
+        }
+        
+        for (int i = n-2; i>=0; i--) {
+            largest[i] = max(largest[i+1], prices[i]); 
+        }
+        
+        // Logic
+        // Max difference b/w the smallest and largest element 
+        int res = 0;
+        for(int i=0; i<n; i++) res = max(res, largest[i]-smallest[i]);
+        
+        return res;
+        
+    }       
+};