Created candy.cpp

src/cpp/candy.cpp

@@ -0,0 +1,29 @@
+// https://leetcode.com/problems/candy/
+
+/*
+The input is interpreted as consisting of "hills" and "valleys" . All valleys will greedily have 1 candy and the no of 
+candies will gradually increase by 1 for each level we move up from this valley . A valley will contribute to the answer 
+of both hills to its left as well as to it's right , so traversing the input twice once in forward direction and one in 
+reverse and then taking the maximum of the 2 contributions will give us the answer.
+*/
+
+class Solution {
+public:
+    int candy(vector<int>& ratings) {
+     int n=ratings.size();
+     int pre[n],suf[n];
+      pre[0]=1;
+      for(int i=1;i<n;i++){
+          if(ratings[i]>ratings[i-1])pre[i]=pre[i-1]+1;     // we climb 1 level on the hill to the right
+          else pre[i]=1;
+      }
+       suf[n-1]=1;
+        for(int i=n-2;i>-1;i--){
+            if(ratings[i]>ratings[i+1])suf[i]=suf[i+1]+1;    // we climb 1 level on the hill to the left
+            else suf[i]=1;
+        }
+        int ans=0;
+        for(int i=0;i<n;i++)ans+=max(suf[i],pre[i]);
+        return ans;
+    }
+};