tyvj1305（最大子序列和————单调队列）

Posted 2020-11-02 lmjer

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;

const int maxn=1000000;

int q[maxn],a[maxn];

int main(){
    int n;
    int m;
    scanf("%d%d",&n,&m);
    for (int i=1;i<=n;i++){
        scanf("%d",&a[i]);
    }
    for (int i=1;i<=n;i++){
        a[i]+=a[i-1];
    }
    int l,r;
    l=r=1;
    q[l]=0;
    int ans=-(0x3f3f3f3f);
    for (int i=1;i<=n;i++){
        while(l<=r&&q[l]<i-m) l++;//保证答案的合法性
        ans=max(ans,a[i]-a[q[l]]);//因为保证了队列的单调性，所以队头元素为当前最优
        while(l<=r&&a[q[r]]>=a[i]) r--;//保证队列的单调性,即保证队头答案最优
        q[++r]=i;
    }
    printf("%d\n",ans);
return 0;
}