HDU 1754 I Hate It

来源：互联网发布：抓小三软件编辑：程序博客网时间：2024/06/10 18:30

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分析：继续单点更新、学线段树的时候尽量不要去看模板、自己慢慢分析、那样才是真的学会了、尽管变形依然能做出来、单点更新先就做到这里、

#include<stdio.h>#include<string.h>#define N 200005struct node{    int l,r;    int max;}tree[N<<2];int a[N];int n,ans;int maxx(int a,int b){    if(a>b)return a;    return b;}void create(int x,int l,int r){    tree[x].l=l;    tree[x].r=r;    int mid=(l+r)/2;    if(l==r){        tree[x].max=a[l];        return;    }    create(x*2,l,mid);    create(x*2+1,mid+1,r);    tree[x].max=maxx(tree[x*2].max,tree[x*2+1].max);}void update(int x,int p,int num){    if(tree[x].l==p&&tree[x].r==p){        tree[x].max=num;        return;    }    int mid=(tree[x].l+tree[x].r)/2;    if(p<=mid)        update(x*2,p,num);    else        update(x*2+1,p,num);    tree[x].max=maxx(tree[x*2].max,tree[x*2+1].max);}void query(int x,int l,int r){    if(tree[x].l==l&&tree[x].r==r){        ans=maxx(ans,tree[x].max);        return;    }    int mid=(tree[x].l+tree[x].r)/2;    if(l>mid)        query(x*2+1,l,r);    else if(r<=mid)        query(x*2,l,r);    else{        query(x*2,l,mid);        query(x*2+1,mid+1,r);    }}int main(){    int m,i,x,y;    char ch[5];    while(scanf("%d%d",&n,&m)!=EOF){        memset(a,0,sizeof(a));        for(i=1;i<=n ;i++)            scanf("%d",&a[i]);        create(1,1,n);        while(m--){            scanf("%s%d%d",ch,&x,&y);            if(ch[0]=='U'){                update(1,x,y);            }            if(ch[0]=='Q'){                ans=0;                query(1,x,y);                printf("%d\n",ans);            }        }    }    return 0;}