<p>There are <code>n</code> children standing in a line. Each child is assigned a rating value given in the integer array <code>ratings</code>.</p>

<p>You are giving candies to these children subjected to the following requirements:</p>

<ul>
	<li>Each child must have at least one candy.</li>
	<li>Children with a higher rating get more candies than their neighbors.</li>
</ul>

<p>Return <em>the minimum number of candies you need to have to distribute the candies to the children</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

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

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> ratings = [1,2,2]
<strong>Output:</strong> 4
<strong>Explanation:</strong> 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.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>n == ratings.length</code></li>
	<li><code>1 &lt;= n &lt;= 2 * 10<sup>4</sup></code></li>
	<li><code>0 &lt;= ratings[i] &lt;= 2 * 10<sup>4</sup></code></li>
</ul>

class Solution {
public:
    int candy(vector<int>& ratings) {
        if(!ratings.size()) return 0;
        if(ratings.size()==1) return 1;
        int sum=1;
        bool isRev = false;
        int lastMax = 1;
        vector<int> candy;
        candy.push_back(1);
        for(int i=1;i<ratings.size();i++){
            if(ratings[i]>ratings[i-1]){
                if(!isRev){
                    sum+=candy[i-1]+1;
                    candy.push_back(candy[i-1]+1);
                }else{
                    sum+=2;
                    candy.push_back(2);
                }
                isRev = false;
            }else if(ratings[i]==ratings[i-1]){
                sum+=1;
                candy.push_back(1);
                isRev = false;
            }else{
                if(!isRev&&candy[i-1]==1){
                    sum+=2;
                    lastMax = 1;
                    candy.push_back(2);
                }else if(!isRev){
                    sum+=1;
                    lastMax = candy[candy.size()-1];
                    candy.push_back(1);
                }else{
                    if(candy[i-1]==lastMax-1){
                        sum+=candy[i-1]+2;
                        lastMax++;
                    }else{
                        sum+=candy[i-1]+1;
                    }
                    candy.push_back(candy[i-1]+1);
                }
                isRev = true;
            }
        }
        return sum;
    }
};
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