gistfile1.txt

LEETCODE CANDY QUESTION
QUES NO. 135

Question-
There are n children standing in a line. Each child is assigned a rating value given in the integer array ratings.

You are giving candies to these children subjected to the following requirements:

Each child must have at least one candy.
Children with a higher rating get more candies than their neighbors.
Return the minimum number of candies you need to have to distribute the candies to the children.

Mistake I did initially - earlier I was overwriting some values in the second pass. which I fixed later.

Example 1:

Input: ratings = [1,0,2]
Output: 5
Explanation: You can allocate to the first, second and third child with 2, 1, 2 candies respectively.
Example 2:

Input: ratings = [1,2,2]
Output: 4
Explanation: You can allocate to the first, second and third child with 1, 2, 1 candies respectively.
The third child gets 1 candy because it satisfies the above two conditions.
 

Constraints:

n == ratings.length
1 <= n <= 2 * 104
0 <= ratings[i] <= 2 * 104

Solution-
class Solution {
public:
//two pass greedy solution.
    int candy(vector<int>& ratings) {
        int n=ratings.size();
        if(n==1) return 1;
        int sum=0;
        vector<int> temp(n,1);
        for(int i=1;i<n;i++){
            if(ratings[i]>ratings[i-1]){
                temp[i]=temp[i-1]+1;
            }
        }
        for(int i=n-2;i>=0;i--){
            if(ratings[i]>ratings[i+1]){
                temp[i]=max(temp[i],temp[i+1]+1);
            }
            sum+=temp[i];
        }
        sum+=temp[n-1];
        return sum;
    }
};

this is a C++ code.