入门级数据结构算法。复习一下，分别手写一个。
线段树版本（过了CF上的https://codeforces.com/contest/1291/problem/D）：
1 #include<bits/stdc++.h>
2 #define f(i,a,b) for(int i=a;i<=b;i++)
3 using namespace std;
4 struct qujian{
5 int l,r,index;
6 friend bool operator < (const qujian q1,const qujian q2){
7 return q1.r<q2.r;
8 }
9 }qu[100005];
10 int q;
11
12 const int N=2e5+5;
13 int a[N];
14 struct node{
15 int l,r,val;
16 }tree[N<<2];
17 void build(int rt,int l,int r){
18 tree[rt].l=l,tree[rt].r=r;
19 if(l==r){
20 tree[rt].val=0;
21 return;
22 }
23 int mid=l+r>>1;
24 build(rt<<1,l,mid);
25 build(rt<<1|1,mid+1,r);
26 tree[rt].val=tree[rt<<1].val+tree[rt<<1|1].val;
27 }
28 void update(int rt,int pos,int val){
29 if(tree[rt].l==tree[rt].r&&pos==tree[rt].l){
30 tree[rt].val+=val;
31 return;
32 }
33 int mid=tree[rt].l+tree[rt].r>>1;
34 if(pos<=mid) update(rt<<1,pos,val);
35 else update(rt<<1|1,pos,val);
36 tree[rt].val+=val;
37 }
38 int query(int rt,int l,int r){
39 if(l<=tree[rt].l&&r>=tree[rt].r) return tree[rt].val;
40 int mid=tree[rt].l+tree[rt].r>>1;
41 if(l>mid) return query(rt<<1|1,l,r);
42 else if(r<=mid) return query(rt<<1,l,r);
43 else return query(rt<<1,l,mid)+query(rt<<1|1,mid+1,r);
44 }
45
46 map<char,int> mp;
47 char b[N];
48 int ans[N];
49
50 bool cmp(const qujian q1,const qujian q2){
51 return q1.index<q2.index;
52 }
53
54 int main(){
55 scanf("%s",b+1);
56 int len=strlen(b+1);
57 scanf("%d",&q);
58 f(i,1,q) scanf("%d%d",&qu[i].l,&qu[i].r),qu[i].index=i;
59 sort(qu+1,qu+1+q);
60 //f(i,1,q) cout<<qu[i].l<<" "<<qu[i].r<<endl;
61 int cur=1;
62 build(1,1,len);
63 f(i,1,q){
64 f(j,cur,qu[i].r){
65 //cout<<"the current qujian is "<<qu[i].l<<" "<<qu[i].r<<endl;
66 int p=mp[b[j]];
67 if(p!=0){
68 update(1,p,-1);
69 //cout<<b[j]<<" has appeared at "<<p<<endl;
70 }
71 update(1,j,1);
72 //cout<<b[j]<<" last appeared at "<<j<<endl;
73 //cout<<"now the "<<j<<" is "<<query(1,j,j)<<endl;
74 mp[b[j]]=j;
75 }
76 cur=qu[i].r+1;
77 ans[qu[i].index]=query(1,qu[i].l,qu[i].r);
78 //cout<<qu[i].index<<":["<<qu[i].l<<","<<qu[i].r<<"]="<<query(1,qu[i].l,qu[i].r)<<endl;
79 }
80 //f(i,1,q) cout<<ans[i]<<" ";
81 sort(qu+1,qu+1+q,cmp);
82 f(i,1,q){
83 if(qu[i].r-qu[i].l+1==1){
84 puts("YES");
85 }
86 else if(ans[i]>=3){
87 puts("YES");
88 }
89 else if(b[qu[i].l]!=b[qu[i].r]){
90 puts("YES");
91 }
92 else puts("NO");
93 }
94 }
树状数组版本（怪不得潘神这么喜欢，写起来确实短得多）：
1 #include<bits/stdc++.h>
2 #define f(i,a,b) for(int i=a;i<=b;i++)
3 using namespace std;
4 struct qujian{
5 int l,r,index;
6 friend bool operator < (const qujian q1,const qujian q2){
7 return q1.r<q2.r;
8 }
9 }qu[100005];
10 bool cmp(const qujian q1,const qujian q2){
11 return q1.index<q2.index;
12 }
13 const int N=1e5+5;
14 map<int,int> mp;
15 int ans[N];
16 int len[N];
17 int n,q;
18 int a[N];
19 int tree[N];
20 #define lowbit(x) (x&(-x))
21 void update(int pos,int val){
22 while(pos<=n){
23 tree[pos]+=val;
24 pos+=lowbit(pos);
25 }
26 }
27 int sum_1_to_pos(int pos){
28 int ans=0;
29 while(pos>0){
30 ans+=tree[pos];
31 pos-=lowbit(pos);
32 }
33 return ans;
34 }
35 #define query(x,y) (sum_1_to_pos(y)-sum_1_to_pos(x-1))
36
37 int main(){
38 scanf("%d%d",&n,&q);
39 f(i,1,n) scanf("%d",&a[i]);
40 f(i,1,q) scanf("%d%d",&qu[i].l,&qu[i].r),qu[i].index=i,len[i]=qu[i].r-qu[i].l+1;
41 sort(qu+1,qu+1+q);
42 int cur=1;
43 f(i,1,q){
44 f(j,cur,qu[i].r){
45 int p=mp[a[j]];
46 if(p!=0){
47 update(p,-1);
48 }
49 update(j,1);
50 mp[a[j]]=j;
51 }
52 cur=qu[i].r+1;
53 ans[qu[i].index]=query(qu[i].l,qu[i].r);
54 }
55 f(i,1,q){
56 if(ans[i]==len[i]) puts("Yes");
57 else puts("No");
58 }
59 }
原文地址：https://www.cnblogs.com/St-Lovaer/p/12261657.html
时间： 2024-10-16 02:44:38