codeforces 522D. Closest Equals 线段树+离线

题目链接

n个数m个询问， 每次询问输出给定区间中任意两个相同的数的最近距离。

先将询问读进来， 然后按r从小到大排序， 将n个数按顺序插入， 并用map统计之前是否出现过， 如果出现过， 就更新线段树。

如果当前的i等于某个询问的r， 那么就查询， 具体看代码。

 #include <iostream>
 #include <vector>
 #include <cstdio>
 #include <cstring>
 #include <algorithm>
 #include <cmath>
 #include <map>
 #include <set>
 #include <string>
 #include <queue>
 #include <stack>
 #include <bitset>
 using namespace std;
 #define pb(x) push_back(x)
 #define ll long long
 #define mk(x, y) make_pair(x, y)
 #define lson l, m, rt<<1
 #define mem(a) memset(a, 0, sizeof(a))
 #define rson m+1, r, rt<<1|1
 #define mem1(a) memset(a, -1, sizeof(a))
 #define mem2(a) memset(a, 0x3f, sizeof(a))
 #define rep(i, n, a) for(int i = a; i<n; i++)
 #define fi first
 #define se second
 typedef pair<int, int> pll;
 const double PI = acos(-1.0);
 const double eps = 1e-;
 const int mod = 1e9+;
 const int inf = ;
 const int dir[][] = { {-, }, {, }, {, -}, {, } };
 const int maxn = 5e5+;
 int minn[maxn<<], a[maxn], ans1[maxn], ans;
 struct node
 {
     int l, r, id;
     bool operator < (node a)const
     {
         if(r == a.r)
             id<a.id;
         return r<a.r;
     }
 }q[maxn];
 map <int, int> mp;
 void pushUp(int rt) {
     minn[rt] = min(minn[rt<<], minn[rt<<|]);
 }
 void update(int p, int val, int l, int r, int rt) {
     if(l == r) {
         minn[rt] = val;
         return ;
     }
     int m = l+r>>;
     if(p<=m)
         update(p, val, lson);
     else
         update(p, val, rson);
     pushUp(rt);
 }
 void query(int L, int R, int l, int r, int rt) {
     if(L<=l&&R>=r) {
         ans = min(ans, minn[rt]);
         return ;
     }
     int m = l+r>>;
     if(L<=m)
         query(L, R, lson);
     if(R>m)
         query(L, R, rson);
 }
 int main()
 {
     int n, m;
     cin>>n>>m;
     for(int i = ; i<=n; i++)
         scanf("%d", &a[i]);
     for(int i = ; i<m; i++) {
         scanf("%d%d", &q[i].l, &q[i].r);
         q[i].id = i;
     }
     sort(q, q+m);
     int pos = ;
     mem2(minn);
     for(int i = ; i<=n; i++) {
         if(mp[a[i]]) {
             update(mp[a[i]], i-mp[a[i]], , n, );
         }
         mp[a[i]] = i;
         while(i == q[pos].r) {
             ans = inf;
             query(q[pos].l, i, , n, );
             if(ans == inf)
                 ans = -;
             ans1[q[pos].id] = ans;
             pos++;
         }
     }
     for(int i = ; i<m; i++)
         cout<<ans1[i]<<" ";
     return ;
 }