Candy Problem


Description

LeetCode Problem 135.

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.

Example 1:

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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:

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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 * 10^4
  • 0 <= ratings[i] <= 2 * 10^4


Sample C++ Code

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int candy(vector<int> &ratings) {
	// Do it in two directions.
	// The first loop makes sure children with a higher rating 
	// get more candy than its left neighbor; the second loop 
	// makes sure children with a higher rating get more candy 
	// than its right neighbor.
	int size=ratings.size();
	if(size<=1)
		return size;
	vector<int> num(size,1);
	for (int i = 1; i < size; i++) {
		if(ratings[i]>ratings[i-1])
			num[i]=num[i-1]+1;
	}
	for (int i= size-1; i>0 ; i--) {
		if(ratings[i-1]>ratings[i])
			num[i-1]=max(num[i]+1,num[i-1]);
	}
	int result=0;
	for (int i = 0; i < size; i++) {
		result+=num[i];
	}
	return result;
}




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