Codeforces #485 C. Three displays

本文介绍了一个关于在一系列不同字体大小的显示屏中找到三个显示屏,使得其字体大小依次递增,并且租金总和最小的问题。文章提供了一段Java代码实现,通过动态规划的方法解决了这一问题。

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C. Three displays
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output

It is the middle of 2018 and Maria Stepanovna, who lives outside Krasnokamensk (a town in Zabaikalsky region), wants to rent three displays to highlight an important problem.

There are nn displays placed along a road, and the ii-th of them can display a text with font size sisi only. Maria Stepanovna wants to rent such three displays with indices i<j<ki<j<k that the font size increases if you move along the road in a particular direction. Namely, the condition si<sj<sksi<sj<sk should be held.

The rent cost is for the ii-th display is cici. Please determine the smallest cost Maria Stepanovna should pay.

Input

The first line contains a single integer nn (3n30003≤n≤3000) — the number of displays.

The second line contains nn integers s1,s2,,sns1,s2,…,sn (1si1091≤si≤109) — the font sizes on the displays in the order they stand along the road.

The third line contains nn integers c1,c2,,cnc1,c2,…,cn (1ci1081≤ci≤108) — the rent costs for each display.

Output

If there are no three displays that satisfy the criteria, print -1. Otherwise print a single integer — the minimum total rent cost of three displays with indices i<j<ki<j<k such that si<sj<sksi<sj<sk.

Examples
input
Copy
5
2 4 5 4 10
40 30 20 10 40
output
Copy
90
input
Copy
3
100 101 100
2 4 5
output
Copy
-1
input
Copy
10
1 2 3 4 5 6 7 8 9 10
10 13 11 14 15 12 13 13 18 13
output
Copy
33
Note

In the first example you can, for example, choose displays 1144 and 55, because s1<s4<s5s1<s4<s5 (2<4<102<4<10), and the rent cost is 40+10+40=9040+10+40=90.

In the second example you can't select a valid triple of indices, so the answer is -1.

代码:

public class Main {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
int n = scan.nextInt();
int[] a = new int[n];
int[] cost = new int[n];
for(int i = 0; i < n; i++){
a[i] = scan.nextInt();
}
for(int i = 0; i < n; i++){
cost[i] = scan.nextInt();
}
int[] ans = new int[n];
Arrays.fill(ans, -1);

for(int i = 0; i < n-1; i++){
boolean f = false;
for(int j = i-1; j >= 0; j--){
if(a[i]>a[j]&&!f){
ans[i] = cost[i]+cost[j];
f = true;
}else if(a[i]>a[j]&&f){
ans[i] = Math.min(ans[i], cost[i]+cost[j]);
}
}

}
int min = Integer.MAX_VALUE;
for(int i = 0; i < n; i++){
for(int j = i-1; j >= 0; j--){
if(a[i]>a[j]&&ans[j]!=-1){
min = Math.min(min, ans[j]+cost[i]);

}
}
}

if(min == Integer.MAX_VALUE){
System.out.println("-1");
}else{
System.out.println(min);
}
}
}

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