Function candies

cpp/Greedy/candies.cpp:5–28

#include <algorithm>

int candies(std::vector<int>& ratings) {
    int n = ratings.size();
    // Ensure each child starts with 1 candy.
    std::vector<int> candies(n, 1);
    // First pass: for each child, ensure the child has more candies
    // than their left-side neighbor if the current child's rating is
    // higher.
    for (int i = 1; i < n; i++) {
        if (ratings[i] > ratings[i - 1]) {
            candies[i] = candies[i - 1] + 1;
        }
    }
    // Second pass: for each child, ensure the child has more candies
    // than their right-side neighbor if the current child's rating is
    // higher.
    for (int i = n - 2; i >= 0; i--) {
        if (ratings[i] > ratings[i + 1]) {
            // If the current child already has more candies than their
            // right-side neighbor, keep the higher amount.
            candies[i] = std::max(candies[i], candies[i + 1] + 1);
        }
    }
    return std::accumulate(candies.begin(), candies.end(), 0);
}