技術標籤：圖論LeetCode

Description

Solution
以孩子間的關係建單向邊，每個點在拓撲排序中的層數之和即為答案

Hint
評分相同的孩子需要建雙向邊

Code

class Solution {
public:
    #define maxn 200005
    int d[maxn];
    vector<int>edge[maxn];
    inline void add(int u,int v) {
        edge[u].push_back(v);
        d[v]++;
    }
    int candy(vector<
 
int>& ratings) {
        int n =  ratings.size();
        for(int i = 0;i < n;++i) edge[i].clear(), d[i] = 0;
        for(int i = 0;i < n;++i) {
            if(i != n-1) {
                if(ratings[i] > ratings[i+1]) add(i+1,i);
                if(ratings[i] < ratings[i+1]) add(i,i+
 
1);
            }
            if(i != 0) {
                if(ratings[i] > ratings[i-1]) add(i-1,i);
                if(ratings[i] < ratings[i-1]) add(i,i-1);
            }
        }
        queue<int>q;
        int cnt = 1, res = 0;
        for(int i = 0;i < n;++i) if(d[i]==0) q.push(i),
 
q.push(cnt);
        while(!q.empty()) {
            int now = q.front();q.pop();
            cnt = q.front();q.pop();
            res += cnt;
            for(auto v : edge[now]) {
                if(--d[v] == 0) q.push(v), q.push(cnt+1);
            }
        }return res;
    }
};