#include<iostream> #include<cstdio> #include<cstring> #include<algorithm> #define lson l,m,rt<<1 #define rson m+1,r,rt<<1|1 #define maxn 2222222 using namespace std; int a[maxn<<2]; void pushUp(int rt) { a[rt]=max(a[rt<<1],a[rt<<1|1]); } void build(int l,int r,int rt) { if(l==r) { scanf("%d",&a[rt]); return ; } int m=(r+l)>>1; build(lson); build(rson); pushUp(rt); } void update(int p,int sc,int l,int r,int rt) { if(l==r) { a[rt]=sc; return; } int m=(l+r)>>1; if(p<=m) update(p,sc,lson); else update(p,sc,rson); pushUp(rt); } int query(int L,int R,int l,int r,int rt) { int x=0; if(L<=l&&r<=R) return a[rt]; int m=(r+l)>>1; if(L<=m) x=max(x,query(L,R,lson)); if(R>m) x=max(x,query(L,R,rson)); return x; } int main() { int n,m; while(scanf("%d%d",&n,&m)!=EOF) { build(1,n,1); char c[2]; int d,e; for(int i=0; i<m; i++) { scanf("%s%d%d",c,&d,&e); if(c[0]=='Q') { printf("%d ",query(d,e,1,n,1)); } if(c[0]=='U') { update(d,e,1,n,1); } } } return 0; }
hdu_1754,线段树单点更新,求区间最值
http://www.notonlysuccess.com/index.php/segment-tree-complete/