【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

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  }