线段树

参考资料：http://www.notonlysuccess.com/index.php/segment-tree-complete/

hdu1166

题意：对于n（n≤500000），操作有两种：①任意更改某个点的值②求任意区间的和

#include <stdio.h>
const int N=50005<<2;
int sum[N];
int T,n;
///rt表示当前子树的根(root),也就是当前所在的结点
void PushUP(int rt){
    sum[rt]=sum[rt<<1]+sum[rt<<1|1];
}
void build(int left,int right,int rt){
    if(left==right) {
        scanf("%d",&sum[rt]);
        return ;
    }
    int mid=(left+right)>>1;
    build(left,mid,rt<<1);
    build(mid+1,right,rt<<1|1);
    PushUP(rt);
}
void update(int p,int add,int left,int right,int rt){
    if(left==right) {
        sum[rt]+=add;
        return ;
    }
    int mid=(left+right)>>1;
    if(p<=mid) update(p,add,left,mid,rt<<1);
    else update(p,add,mid+1,right,rt<<1|1);
    PushUP(rt);
}
int query(int L,int R,int left,int right,int rt){
    if(L<=left&&right<=R){
        return sum[rt];
    }
    int mid=(left+right)>>1;
    int ret=0;
    if(L<=mid) ret+=query(L,R,left,mid,rt<<1);
    if(R>mid) ret+=query(L,R,mid+1,right,rt<<1|1);
    return ret;
}
int main(){
    int i,j,cas=1;
    char ch[10];
    while(scanf("%d",&T)!=EOF)
    while(T--){
        scanf("%d",&n);
        build(1,n,1);
        printf("Case %d:\n",cas++);
        while(scanf("%s",ch)){
            if(ch[0]=='E') break;
            scanf("%d%d",&i,&j);
            if(ch[0]=='Q') printf("%d\n",query(i,j,1,n,1));
            else if(ch[0]=='S') update(i,-j,1,n,1);
            else update(i,j,1,n,1);
        }
    }
    return 0;
}

hdu1754

题意：区间求最值

#include <stdio.h>
const int N=200005<<2;
int Max[N];
int q,n;
///rt表示当前子树的根(root),也就是当前所在的结点
int max(int a,int b){return a>b?a:b;}
void PushUP(int rt){
    Max[rt]=max(Max[rt<<1],Max[rt<<1|1]);
}
void build(int left,int right,int rt){
    if(left==right) {
        scanf("%d",&Max[rt]);
        return ;
    }
    int mid=(left+right)>>1;
    build(left,mid,rt<<1);
    build(mid+1,right,rt<<1|1);
    PushUP(rt);
}
void update(int p,int sc,int left,int right,int rt){
    if(left==right) {
        Max[rt]=sc;
        return ;
    }
    int mid=(left+right)>>1;
    if(p<=mid) update(p,sc,left,mid,rt<<1);
    else update(p,sc,mid+1,right,rt<<1|1);
    PushUP(rt);
}
int query(int L,int R,int left,int right,int rt){
    if(L<=left&&right<=R){
        return Max[rt];
    }
    int mid=(left+right)>>1;
    int ret=0;
    if(L<=mid) ret=max(ret,query(L,R,left,mid,rt<<1));
    if(R>mid) ret=max(ret,query(L,R,mid+1,right,rt<<1|1));
    return ret;
}
int main(){
    int i,j;
    char ch[10];
    while(scanf("%d%d",&n,&q)!=EOF){
        build(1,n,1);
        while(q--){
            scanf("%s",ch);
            scanf("%d%d",&i,&j);
            if(ch[0]=='Q') printf("%d\n",query(i,j,1,n,1));
            else update(i,j,1,n,1);
        }
    }
    return 0;
}

hrbustoj1752

题意：求最值，输出下角标

#include <stdio.h>
const int N=100005<<2;
struct T{
    int idx;
    int Max;
}t[N];
int q,n;
///rt表示当前子树的根(root),也就是当前所在的结点
T max(T t1,T t2){
    if(t1.Max!=t2.Max) return t1.Max>t2.Max?t1:t2;
    else return t1.idx>t2.idx?t1:t2;
}
void PushUP(int rt){
    t[rt]=max(t[rt<<1],t[rt<<1|1]);
}
void build(int left,int right,int rt){
    if(left==right) {
        scanf("%d",&t[rt].Max);
        t[rt].idx=left;
        return ;
    }
    int mid=(left+right)>>1;
    build(left,mid,rt<<1);
    build(mid+1,right,rt<<1|1);
    PushUP(rt);
}
void update(int p,int sc,int left,int right,int rt){
    if(left==right) {
        t[rt].Max=sc;
        return ;
    }
    int mid=(left+right)>>1;
    if(p<=mid) update(p,sc,left,mid,rt<<1);
    else update(p,sc,mid+1,right,rt<<1|1);
    PushUP(rt);
}
T query(int L,int R,int left,int right,int rt){
    if(L<=left&&right<=R){
        return t[rt];
    }
    int mid=(left+right)>>1;
    T ret;ret.Max=0;
    if(L<=mid) ret=max(ret,query(L,R,left,mid,rt<<1));
    if(R>mid) ret=max(ret,query(L,R,mid+1,right,rt<<1|1));
    return ret;
}
int main(){
    int i,j;
    char ch[10];
    while(scanf("%d",&n)!=EOF){
        build(1,n,1);
        scanf("%d",&q);
        while(q--){
            scanf("%s",ch);
            if(ch[0]=='Q') {
                T tmp=query(1,n,1,n,1);
                printf("%d %d\n",tmp.idx,tmp.Max);
            }
            else {
                scanf("%d%d",&i,&j);
                update(i,j,1,n,1);
            }
        }
        puts("");
    }
    return 0;
}

这道题或者用堆，或者用优先队列

#include <stdio.h>
#include <queue>
#include <iostream>
using namespace std;
struct info{
    int idx;
    int key;
    bool operator < (const info &a) const {
        if(a.key!=key) return a.key>key;
        else return a.idx>idx;
    }
};
int f[100005];
int main(){
    int n,q;
    int i,j,k;
    info now;
    char ch;
    while(scanf("%d",&n)!=EOF){
        priority_queue<info>pq;
        for(i=1;i<=n;++i){
            scanf("%d",&f[i]);
            now.idx=i;
            now.key=f[i];
            pq.push(now);
        }
        scanf("%d",&q);
        while(q--){
            getchar();
            scanf("%c",&ch);
            if(ch=='Q') {
                while(f[pq.top().idx]!=pq.top().key){
                    pq.pop();
                }
                printf("%d %d\n",pq.top().idx,pq.top().key);
            }
            else{
                scanf("%d %d",&i,&j);
                f[i]=j;
                now.idx=i;
                now.key=j;
                pq.push(now);
            }
        }
        puts("");
    }
    return 0;
}