LeetCode 860. Lemonade Change (lemonade give change)

Topic Tags: Greedy

　　When the time to receive the $ 5, Five count;

　　When you receive $ 10 of time, came with five zero;

　　When you receive $ 20 when the first came with ten to zero, if not, then five come to zero.

　　If the process, five less than 0, indicating not enough money to give change, fail.

 

Java Solution:

Runtime:  2 ms, faster than 81.80% 

Memory Usage: 42.1 MB, less than 7.69%

Completion Date: 02/15/2020

Key: setting five, ten counting

class Solution {
    public boolean lemonadeChange(int[] bills) {
        int five = 0, ten = 0;
        
        for(int b : bills) {
            if(b == 5) {
                five++;
            }
            else if(b == 10) {
                five--;
                ten++;
            }
            else if(b == 20) {
                if(ten > 0) { // use ten first
                    ten--;
                    five--;
                }
                else {
                    five -= 3;
                }
            }
            
            if(five < 0)
                return false;
        }
        
        return true;
    }
}

Reference: LeetCode discuss

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