SPOJ 1716 Can you answer these queries III(GSS3 线段树)
2012-09-15 19:47
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by---cxlove
题目:求出最大子段和,有更新操作,将某个数修改
http://www.spoj.pl/problems/GSS3/
和GSS1类似/article/2566090.html
不过sum值不好更新,就放线段树里更新算了,GSS1写得效率就低, 哭~~~
没啥好说的,单点更新,直接到叶子,然后一层层Push_Up
by---cxlove
题目:求出最大子段和,有更新操作,将某个数修改
http://www.spoj.pl/problems/GSS3/
和GSS1类似/article/2566090.html
不过sum值不好更新,就放线段树里更新算了,GSS1写得效率就低, 哭~~~
没啥好说的,单点更新,直接到叶子,然后一层层Push_Up
#include<iostream> #include<cstdio> #include<map> #include<cstring> #include<cmath> #include<vector> #include<queue> #include<algorithm> #include<set> #define inf (1ull<<63)-1 #define N 50005 #define maxn 100005 #define Min(a,b) ((a)<(b)?(a):(b)) #define Max(a,b) ((a)>(b)?(a):(b)) #define pb(a) push_back(a) #define mem(a,b) memset(a,b,sizeof(a)) #define eps 1e-9 #define zero(a) fabs(a)<eps #define LL long long #define ULL unsigned long long #define lson (step<<1) #define rson (step<<1|1) #define MOD 1000000007 #define mp(a,b) make_pair(a,b) using namespace std; int n,a ,q,sum ={0}; struct Node{ int left,right,lx,rx,mx,sum; }L[N*4]; void Push_Up(int step){ L[step].lx=max(L[lson].lx,L[lson].sum+L[rson].lx); L[step].rx=max(L[rson].rx,L[rson].sum+L[lson].rx); L[step].mx=max(max(L[lson].mx,L[rson].mx),L[lson].rx+L[rson].lx); L[step].sum=L[lson].sum+L[rson].sum; } void Bulid(int step,int l,int r){ L[step].left=l;L[step].right=r; if(l==r){ L[step].lx=L[step].rx=L[step].mx=L[step].sum=a[l]; return ; } int m=(l+r)/2; Bulid(lson,l,m); Bulid(rson,m+1,r); Push_Up(step); } int Q_L(int step,int l,int r){ if(L[step].left==l&&L[step].right==r) return L[step].lx; int m=(L[step].left+L[step].right)/2; if(r<=m) return Q_L(lson,l,r); else if(l>m) return Q_L(rson,l,r); else return max(Q_L(lson,l,m),max(L[lson].sum,L[lson].sum+Q_L(rson,m+1,r))); } int Q_R(int step,int l,int r){ if(L[step].left==l&&L[step].right==r) return L[step].rx; int m=(L[step].left+L[step].right)/2; if(r<=m) return Q_R(lson,l,r); else if(l>m) return Q_R(rson,l,r); else return max(Q_R(rson,m+1,r),max(L[rson].sum,L[rson].sum+Q_R(lson,l,m))); } int Query(int step,int l,int r){ if(L[step].left==l&&L[step].right==r) return L[step].mx; int m=(L[step].left+L[step].right)/2; if(r<=m) return Query(lson,l,r); else if(l>m) return Query(rson,l,r); else return max(max(Query(lson,l,m),Query(rson,m+1,r)),Q_R(lson,l,m)+Q_L(rson,m+1,r)); } void Update(int step,int pos,int c){ if(L[step].left==L[step].right){ L[step].mx+=c; L[step].rx+=c; L[step].lx+=c; L[step].sum+=c; return ; } int m=(L[step].left+L[step].right)/2; if(pos<=m) Update(lson,pos,c); else Update(rson,pos,c); Push_Up(step); } int main(){ while(scanf("%d",&n)!=EOF){ for(int i=1;i<=n;i++) scanf("%d",&a[i]); Bulid(1,1,n); scanf("%d",&q); while(q--){ int k,l,r; scanf("%d%d%d",&k,&l,&r); if(k==0) {Update(1,l,r-a[l]);a[l]=r;} else printf("%d\n",Query(1,l,r)); } } return 0; }
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