135. Candy[hard]

135. Candy

There are N children standing in a line. Each child is assigned a rating value.

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.
What is the minimum candies you must give?

先对ratings进行排序，从小到大发糖果。

发糖果时判断：左右两边的人是否分数比自己小，若是，则糖果数比他们大即可。

细节：两个人分数一样时糖果数不一定一样。

class Solution
{
public:
int n;
int * c;
vector<pair<int,int>> a;

int candy( vector< int >& ratings)
{
n = ratings.size();
c = (int*)calloc(n + 10, sizeof(int));

for(int i = 0 ; i < n ; i++)
a.push_back( make_pair( ratings[ i ] , i ) );
sort( a.begin() , a.end() );

int ans = 0 ;
for(int i = 0; i < n; ++ i)
{
int x = a[i].second;
c[x] = 1;

if (x > 0 && c[x - 1] && ratings[x] > ratings[x - 1])
c[x] = c[x - 1] + 1;

if (x < n - 1 && c[x + 1] && ratings[x] > ratings[x + 1])
c[x] = max(c[x], c[x + 1] + 1);

ans += c[x];
}
return ans;
}
};