Codeforces round #256 (Div. 2/C)/codeforces448c_painting fence (grouping)

Solution report

Color the fence. The minimum number of steps is required. you should understand how to color the fence. A brush can be painted horizontally or vertically. You cannot skip the brush ,,,

If it is a vertical brush, it should be the number of fences, if it is a horizontal brush, It is the length of the shortest board, and then consider the board without a brush ,,,

Recursive call ,,,

#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>#define inf 999999999999999using namespace std;long long n,num[5010],tt;void dfs(long long s,long long t){    long long ma=0,mi=inf;    int i,j;    for(i=s; i<=t; i++)    {        if(ma<num[i])            ma=num[i];        if(mi>num[i])            mi=num[i];    }    if(mi==ma)    {        tt+=min(mi,t-s+1);        return ;    }    for(i=s; i<=t; i++)        num[i]-=mi;    tt+=min(mi,t-s);    for(i=s; i<=t; i++)    {        if(num[i]>0)        {            for(j=i; j<=t; j++)            {                if(num[j]==0||(j==t&&num[j]>0))                {                    long long  kk=tt;                    if(j==t&&num[j]>0)                    {                        dfs(i,j);                        if(tt-kk>(j-i+1))                            tt=kk+(j-i+1);                    }                    else                    {                        dfs(i,j-1);                        if(tt-kk>(j-i))                            tt=kk+(j-i);                    }                    i=j;                    break;                }            }        }    }}int main(){    int i,j;    scanf("%lld",&n);    for(i=1; i<=n; i++)        scanf("%lld",&num[i]);    dfs(1,n);    printf("%lld\n",min(tt,n));    return 0;}

Painting fencetime limit per test1 secondmemory limit per test512 megabytesinputstandard inputoutputstandard output

Bizon the champion isn' t just attentive, he also is very hardworking.

Bizon the champion decided to paint his old fence his favorite color, orange. The fence is representedNVertical planks, put in a row. Adjacent planks have no gap between them. The planks are numbered from the left to the right starting from one,I-Th plank has the width of 1 meter and the heightAIMeters.

Bizon the champion bought a brush in the shop, the brush's width is 1 meter. he can make vertical and horizontal strokes with the brush. during a stroke the brush's full surface must touch the fence at all the time (see the samples for the better understanding ). what minimum number of strokes shocould Bizon the champion do to fully paint the fence? Note that you are allowed to paint the same area of the fence multiple times.

Input

The first line contains integerN(1? ≤?N? ≤? 5000)-the number of fence planks. The second line containsNSpace-separated IntegersA1 ,?A2 ,?...,?AN(1? ≤?AI? ≤? 109 ).

Output

Print a single integer-the minimum number of strokes needed to paint the whole fence.

Sample test (s) Input

52 2 1 2 1

Output

3

Input

22 2

Output

2

Input

15

Output

1

Note

In the first sample you need to paint the fence in three strokes with the brush: the first stroke goes on height 1 horizontally along all the planks. the second stroke goes on height 2 horizontally and paints the first and second planks and the third stroke (it can be horizontal and vertical) finishes painting the fourth plank.

In the second sample you can paint the fence with two strokes, either two horizontal or two vertical strokes.

In the third sample there is only one plank that can be painted using a single vertical stroke.