LeetCode – Refresh – Candy

Two notes:

1. result at least n candys. Use array scan from beginning and from end.

2. dp[i] = max(dp[i], count++). count++ already record the increasing sequence, dont have to compare with dp[i+1] (or dp[i-1]) + 1

 

class Solution {
public:
    int candy(vector<int> &ratings) {
        int len = ratings.size(), result = len;
        if (len < 2) return len;
        vector<int> dp(len, 0);
        for (int i = 0, count = 1; i < len; i++) {
            if (i > 0 && ratings[i] > ratings[i-1]) {
                dp[i] = max(dp[i], count++);
            } else {
                count = 1;
            }
        }
        for (int i = len-1, count = 1; i >= 0; i--) {
            if (i < len-1 && ratings[i] > ratings[i+1]) {
                dp[i] = max(dp[i], count++);
            } else {
                count = 1;
            }
        }
        for (int i = 0; i < len; i++) {
            result += dp[i];
        }
        return result;
    }
};