4094: [Usaco2013 Dec]Optimal Milking
Time Limit: 10 Sec Memory Limit: 128 MB[Submit][Status][Discuss]
Description
Input
Output
Sample Input
1
2
3
4
5
5 2
2 7
1 10
Sample Output
【樣例解釋】
第1天,最優方案爲2+4=6 ( 方案1+3+2一樣)
第2天,最優方案爲7+4=11
第3天,最優方案爲10+3+2=15
HINT
#include <bits/stdc++.h>
using namespace std;
const int N = 40000 + 5; long long ans;
int tl[N<<2],tr[N<<2],ta[N<<2],tn[N<<2],n,d,a[N];
void update( int k ){
tl[k] = max( tl[k<<1] + tn[k<<1|1], max( ta[k<<1] + tn[k<<1|1], tl[k<<1] + tl[k<<1|1] ) );
tr[k] = max( tn[k<<1] + tr[k<<1|1], max( tn[k<<1] + ta[k<<1|1], tr[k<<1] + tr[k<<1|1] ) );
tn[k] = max( tn[k<<1] + tn[k<<1|1], max( tn[k<<1] + tl[k<<1|1], tr[k<<1] + tn[k<<1|1] ) );
ta[k] = max( ta[k<<1] + tr[k<<1|1], max( tl[k<<1] + tr[k<<1|1], tl[k<<1] + ta[k<<1|1] ) );
}
void build( int k, int l, int r ){
if( l == r ){
ta[k] = a[l]; return;
}
int mid = l + r >> 1;
build( k<<1, l, mid );
build( k<<1|1, mid+1, r );
update( k );
}
void change( int k, int l, int r, int x, int val ){
if( l == r ){ ta[k] = val; return; }
int mid = l + r >> 1;
if( x <= mid ) change( k<<1, l, mid, x, val );
if( x > mid ) change( k<<1|1, mid+1, r, x, val );
update( k );
}
int main(){
scanf( "%d%d", &n, &d );
for( int i = 1; i <= n; i++ ) scanf( "%d", &a[i] );
build( 1, 1, n );
while( d-- ){
int i,m;
scanf( "%d%d", &i, &m );
change( 1, 1, n, i, m );
ans += max( max( tl[1], tr[1] ), max( tn[1], ta[1] ) );
}
printf( "%lld\n", ans );
return 0;
}