Update daily_temperatures.cpp

Author: avidLearnerInProgress

daily_temperatures.cpp

@@ -1,3 +1,43 @@
+class Solution {
+public:
+    vector<int> dailyTemperatures(vector<int>& T) {
+     
+        
+        /*
+            Next greater to right and difference.
+            Start scanning from right end of array.
+        */
+        
+        
+        stack<pair<int, int>> S; // S.top()[0] ==> temperature, S.top()[1] ==> next warmer(>) temperature
+        
+        int n = T.size();
+        vector<int> result(n, 0);
+        
+        for(int i=n-1; i>=0; i--) {
+            
+            //
+            while(!S.empty() and S.top().first <= T[i]) { //if current element is greater than element at top of stack..pop the element until we find next greater element in stack(next warmer temperature)
+                S.pop();
+            }
+            
+            // once we found it, push the difference between current element to its next warmer temperature in result array.
+            if(!S.empty() and T[i] < S.top().first) {
+                result[i] = S.top().second - i;
+            }
+            
+            S.push({T[i], i});
+        }
+        return result;
+
+    }
+};
+
+
+
+/*
+More optimized in terms of time and space.
+
 class Solution {
 public:
     vector<int> dailyTemperatures(vector<int>& T) {
@@ -14,3 +54,4 @@ class Solution {
         return next_greatest;
     }
 };
+*/