【算法系列学习】线段树 单点覆盖，区间查询最大值 [kuangbin带你飞]专题七 线段树 B - I Hate It

https://vjudge.net/contest/66989#overview

  1 #include<iostream>
  2 #include<cstdio>
  3 #include<cstring>
  4 #include<string>
  5 #include<algorithm>
  6 #include<cmath>
  7 #define lson (i<<1)
  8 #define rson (i<<1|1)
  9 
 10 using namespace std;
 11 const int maxn=2e5+5;
 12 int val[maxn];
 13 
 14 struct Seg
 15 {
 16     int l,r,lazy,val;
 17 }tree[maxn<<2];
 18 
 19 void push_up(int i)
 20 {
 21     tree[i].val=max(tree[lson].val,tree[rson].val);
 22 }
 23 
 24 void push_down(int i)
 25 {
 26     if(tree[i].lazy==-1)
 27     {
 28         return;
 29     }
 30     tree[lson].lazy=tree[lson].val=tree[i].lazy;
 31     tree[rson].lazy=tree[rson].val=tree[i].lazy;
 32     tree[i].lazy=-1;
 33 }
 34 
 35 void Build(int l,int r,int i=1)
 36 {
 37     tree[i].l=l;
 38     tree[i].r=r;
 39     tree[i].lazy=-1;
 40     if(l==r)
 41     {
 42         tree[i].val=val[l];
 43         return;
 44     }
 45     push_down(i);
 46     int mid=(tree[i].l+tree[i].r)>>1;
 47     Build(l,mid,lson);
 48     Build(mid+1,r,rson);
 49     push_up(i);
 50 }
 51 
 52 int Query(int l,int r,int i=1)
 53 {
 54     if(tree[i].l==l&&tree[i].r==r)
 55     {
 56         return tree[i].val;
 57     }
 58     push_down(i);
 59     int mid=(tree[i].l+tree[i].r)>>1;
 60     if(r<=mid)
 61     {
 62         return Query(l,r,lson);
 63     }
 64     else if(l>mid)
 65     {
 66         return Query(l,r,rson);
 67     }
 68     else
 69     {
 70         return max(Query(l,mid,lson),Query(mid+1,r,rson));
 71     }
 72 }
 73 
 74 void Setval(int l,int r,int x,int i=1)
 75 {
 76     if(tree[i].l==l&&tree[i].r==r)
 77     {
 78         tree[i].lazy=tree[i].val=x;
 79         return;
 80     }
 81     push_down(i);
 82     int mid=(tree[i].l+tree[i].r)>>1;
 83     if(r<=mid)
 84     {
 85         Setval(l,r,x,lson);
 86     }
 87     else if(l>mid)
 88     {
 89         Setval(l,r,x,rson); 
 90     }
 91     else
 92     {
 93         Setval(l,mid,x,lson);
 94         Setval(mid+1,r,x,rson);
 95     }
 96     push_up(i);
 97  } 
 98 int main()
 99 {
100     int n,m;
101     while(scanf("%d%d",&n,&m)!=EOF)
102     {
103         for(int i=1;i<=n;i++)
104         {
105             scanf("%d",&val[i]);
106         }
107         Build(1,n);
108         char q[20];
109         int a,b;
110         for(int i=1;i<=m;i++)
111         {
112             scanf("%s%d%d",q,&a,&b);
113             if(q[0]=='Q')
114             {
115                 printf("%d\n",Query(a,b));
116             }
117             else
118             {
119                 Setval(a,a,b);
120             }
121         }
122     }
123     return 0;
124  }
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posted @ 2017-04-06 10:34  shulin15  阅读(255)  评论(0)  编辑  收藏  举报