Training algorithm looking for change

Resource constraints

Time limit: 1.0s Memory Limit: 256.0MB

Problem Description

　　There are n individuals are queuing up to buy canteen rambling chicken rice. Each rambling chicken rice for 25 yuan. The strange thing is, everyone hands of only one bill (face value of each note 25, 50 dollars), and a canteen aunt began without any change. Will the canteen aunt could give everyone the change (assuming that the canteen aunt smart enough)

Input Format

　　The first line an integer n, the number of people queuing.

　　Then n integers a [1], a [2 ], ..., a [n]. a [i] represents the value of the hands of the i-th students banknotes (i smaller, more toward the front in the ranks)

Output Format

　　Output YES or NO

Sample input

4
25 25 50 50

Sample Output

YES

Sample input

2
25 100

Sample Output

NO

Sample input

4
25 25 50 100

Sample Output

YES

Scale data and conventions

　　n is not more than 1 million

 

We need to consider a variety of circumstances, namely 25, 50 and 100 yuan three cases.

 1 #include<iostream>
 2 //author:QIANG
 3 using namespace std;
 4 int main(){
 5     int n,s;
 6     cin>>n;
 7     int tf=0,f=0;
 8     int flag=1;
 9     for(int i=0;i<n;i++){
10         cin>>s;
11         if(flag==1){
12             if(s==25){
13                 tf++;
14             }else if(s==50){
15                 if(tf>0){
16                     tf--;
17                     f++;
18                 }else{
19                     flag=0;
20                 }
21             }else{
22                 if(f>0){
23                     f--;
24                     s=s-50;
25                 }
26                 if(s==50){
27                     if(tf>0){
28                         tf--;
29                     }else{
30                         flag=0;
31                     }
32                 }else{
33                     if(tf>=3){
34                         tf=tf-3;
35                     }else{
36                         flag=0;
37                     }
38                 }
39             }
40         }
41     }
42     if(flag==1){
43         cout<<"YES";
44     }else cout<<"NO";
45     return 0; 
46 }