思路：
O（n）建一颗笛卡尔树，再O（n）dfs向上合并答案就行了。
1 #define IOS ios_base::sync_with_stdio(0); cin.tie(0); 2 #include <cstdio>//sprintf islower isupper 3 #include <cstdlib>//malloc exit strcat itoa system("cls") 4 #include <iostream>//pair 5 #include <fstream> 6 #include <bitset> 7 //#include <map> 8 //#include<unordered_map> 9 #include <vector> 10 #include <stack> 11 #include <set> 12 #include <string.h>//strstr substr 13 #include <string> 14 #include <time.h>//srand(((unsigned)time(NULL))); Seed n=rand()%10 - 0~9; 15 #include <cmath> 16 #include <deque> 17 #include <queue>//priority_queue<long long, vector<long long>, greater<long long> > q;//less 18 #include <vector>//emplace_back 19 //#include <math.h> 20 //#include <windows.h>//reverse(a,a+len);// ~ ! ~ ! floor 21 #include <algorithm>//sort + unique : sz=unique(b+1,b+n+1)-(b+1);+nth_element(first, nth, last, compare) 22 using namespace std;//next_permutation(a+1,a+1+n);//prev_permutation 23 #define fo(a,b,c) for(register int a=b;a<=c;++a) 24 #define fr(a,b,c) for(register int a=b;a>=c;--a) 25 #define mem(a,b) memset(a,b,sizeof(a)) 26 #define pr printf 27 #define sc scanf 28 void swapp(long long &a,long long &b); 29 double fabss(double a); 30 long long maxx(long long a,long long b); 31 long long minn(long long a,long long b); 32 long long Del_bit_1(long long n); 33 long long lowbit(long long n); 34 long long abss(long long a); 35 const long long INF=(1LL<<60); 36 const double E=2.718281828; 37 const double PI=acos(-1.0); 38 const long long inf=(1<<29); 39 const double ESP=1e-9; 40 const long long mod=(long long)1e9+7; 41 const long long N=(long long)3e6+10; 42 43 int son[N][2]; 44 long long min_[N],max_[N]; 45 long long a[N]; 46 long long b[N]; 47 int stak[N]; 48 long long ans=-INF; 49 50 void dfs(int rt,int l,int r) 51 { 52 if(son[rt][0])dfs(son[rt][0],l,rt-1); 53 if(son[rt][1])dfs(son[rt][1],rt+1,r); 54 55 long long minl=minn(b[l-1],min_[son[rt][0]]); 56 long long minr=minn(b[rt],min_[son[rt][1]]); 57 long long maxl=maxx(b[l-1],max_[son[rt][0]]); 58 long long maxr=maxx(b[rt],max_[son[rt][1]]); 59 60 max_[rt]=maxx(maxl,maxr); 61 min_[rt]=minn(minl,minr); 62 63 ans=maxx(ans,(maxr-minl)*a[rt]); 64 ans=maxx(ans,(minr-maxl)*a[rt]); 65 } 66 67 int main() 68 { 69 int n; 70 sc("%d",&n); 71 fo(i,1,n)sc("%lld",&a[i]); 72 fo(i,1,n)sc("%lld",&b[i]),b[i]+=b[i-1]; 73 74 long long top=0; 75 fo(i,1,n) 76 { 77 while(top&&a[i]<a[stak[top]]) 78 son[i][0]=stak[top--]; 79 if(top) 80 son[stak[top]][1]=i; 81 stak[++top]=i; 82 } 83 min_[0]=INF,max_[0]=-INF;//注意细节;;... 84 dfs(stak[1],1,n); 85 pr("%lld ",ans); 86 return 0; 87 } 88 89 /**************************************************************************************/ 90 91 long long maxx(long long a,long long b) 92 { 93 return a>b?a:b; 94 } 95 96 void swapp(long long &a,long long &b) 97 { 98 a^=b^=a^=b; 99 } 100 101 long long lowbit(long long n) 102 { 103 return n&(-n); 104 } 105 106 long long Del_bit_1(long long n) 107 { 108 return n&(n-1); 109 } 110 111 long long abss(long long a) 112 { 113 return a>0?a:-a; 114 } 115 116 double fabss(double a) 117 { 118 return a>0?a:-a; 119 } 120 121 long long minn(long long a,long long b) 122 { 123 return a<b?a:b; 124 }