面试经典150题——Day15

一、题目

135. Candy

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

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.
Return the minimum number of candies you need to have to distribute the candies to the children.

Example 1:

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

Input: ratings = [1,2,2]
Output: 4
Explanation: 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.

Constraints:

n == ratings.length
1 <= n <= 2 * 104
0 <= ratings[i] <= 2 * 104

题目来源：leetcode

二、题解

每次处理一边的情况

class Solution {
public:
    int candy(vector<int>& ratings) {
        int n = ratings.size();
        vector<int> candies(n,1);
        //右边比左边大的情况
        for(int i = 1;i < n;i++){
            if(ratings[i] > ratings[i-1]) candies[i] = candies[i-1] + 1;
        }
        //左边比右边大的情况
        for(int i = n - 2;i >= 0;i--){
            if(ratings[i] > ratings[i+1]) candies[i] = max(candies[i],candies[i+1] + 1);
        }
        int res = 0;
        for(int i = 0;i < n;i++){
            res += candies[i];
        }
        return res;
    }
};
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