leetcode 135. 分发糖果

题目：135. 分发糖果 - 力扣（LeetCode）

看数据规模，nlogn的方法足够了。

先排个序，再统计每个位置的最少糖果数即可。

struct Node {
    int value;
    int id;
    int candy = 0;
    Node(int id, int value) {
        this->id = id;
        this->value = value;
    }
};

bool mySort(Node* a, Node* b) {
    return a->value < b->value;
}

class Solution {
public:
    int candy(vector<int>& ratings) {
        int n = ratings.size();
        vector<Node*> arr;
        int sum = 0;
        for (int i = 0; i < n; i++) {
            arr.push_back(new Node(i, ratings[i]));
        }
        
        sort(arr.begin(), arr.end(), mySort);
        int* idx = new int[n];
        for (int i = 0; i < n; i++) {
            idx[arr[i]->id] = i;
        }
        for (int i = 0; i < n; i++) {
            if (arr[i]->candy == 0) {
                arr[i]->candy = 1;
                sum += 1;
            }
            if (arr[i]->id > 0) {
                int left = idx[arr[i]->id - 1];
                if (arr[i]->value < arr[left]->value && arr[i]->candy + 1 > arr[left]->candy) {
                    sum += arr[i]->candy + 1 - arr[left]->candy;
                    arr[left]->candy = arr[i]->candy + 1;
                }
            }
            if (arr[i]->id < n - 1) {
                int right = idx[arr[i]->id + 1];
                if (arr[i]->value < arr[right]->value && arr[i]->candy + 1 > arr[right]->candy) {
                    sum += arr[i]->candy + 1 - arr[right]->candy;
                    arr[right]->candy = arr[i]->candy + 1;
                }
            }
        }
        
        for (int i = 0; i < n; i++) delete arr[i];
        delete [] idx;
        return sum;
    }
};