LeetCode 135. 分发糖果

分情况考虑一下就好了
1.递增前一个直接+1
2.值不变，直接变成1
3.值减少的时候要注意连续递减了多少个，是否要增加前一位的值

class Solution {
public:
    int candy(vector<int>& ratings) {
        int sum = 0 ;
        int pre = 0 ;
        int st = 0 ;
        int i = 0 ;
        while( i < ratings.size() ){
            if( i == 0 ){
                sum += 1 ;
                pre = 1 ;
                st = i ;
            }
            else if( ratings[i] > ratings[i-1] ){
                pre = pre + 1 ;
                sum = sum + pre ;
                st = i ;
            }
            else if( ratings[i] == ratings[i-1]){
                pre = 1 ;
                sum += pre ;
                st = i ;
            }
            else{
                int k = i ;
                while( k < ratings.size() && ratings[k] < ratings[k-1] ){
                    k++ ;
                }
                int m = k - i ;
                sum += ( m * (m+1) / 2 );
                sum += max( 0, m + 1 - pre );
                pre = 1 ;
                i = k ;
                continue ;
            }
            i++ ;
        }
        return sum ;

    }
};