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。

  1 #include <iostream>
  2 #include <vector>
  3 #include <cstdio>
  4 #include <cstring>
  5 #include <algorithm>
  6 #include <cmath>
  7 #include <map>
  8 #include <set>
  9 #include <string>
 10 #include <queue>
 11 #include <stack>
 12 #include <bitset>
 13 using namespace std;
 14 #define pb(x) push_back(x)
 15 #define ll long long
 16 #define mk(x, y) make_pair(x, y)
 17 #define lson l, m, rt<<1
 18 #define mem(a) memset(a, 0, sizeof(a))
 19 #define rson m+1, r, rt<<1|1
 20 #define mem1(a) memset(a, -1, sizeof(a))
 21 #define mem2(a) memset(a, 0x3f, sizeof(a))
 22 #define rep(i, n, a) for(int i = a; i<n; i++)
 23 #define fi first
 24 #define se second
 25 typedef pair<int, int> pll;
 26 const double PI = acos(-1.0);
 27 const double eps = 1e-8;
 28 const int mod = 1e9+7;
 29 const int inf = 1061109567;
 30 const int dir[][2] = { {-1, 0}, {1, 0}, {0, -1}, {0, 1} };
 31 const int maxn = 5e5+5;
 32 int minn[maxn<<2], a[maxn], ans1[maxn], ans;
 33 struct node
 34 {
 35     int l, r, id;
 36     bool operator < (node a)const
 37     {
 38         if(r == a.r)
 39             id<a.id;
 40         return r<a.r;
 41     }
 42 }q[maxn];
 43 map <int, int> mp;
 44 void pushUp(int rt) {
 45     minn[rt] = min(minn[rt<<1], minn[rt<<1|1]);
 46 }
 47 void update(int p, int val, int l, int r, int rt) {
 48     if(l == r) {
 49         minn[rt] = val;
 50         return ;
 51     }
 52     int m = l+r>>1;
 53     if(p<=m)
 54         update(p, val, lson);
 55     else
 56         update(p, val, rson);
 57     pushUp(rt);
 58 }
 59 void query(int L, int R, int l, int r, int rt) {
 60     if(L<=l&&R>=r) {
 61         ans = min(ans, minn[rt]);
 62         return ;
 63     }
 64     int m = l+r>>1;
 65     if(L<=m)
 66         query(L, R, lson);
 67     if(R>m)
 68         query(L, R, rson);
 69 }
 70 int main()
 71 {
 72     int n, m;
 73     cin>>n>>m;
 74     for(int i = 1; i<=n; i++)
 75         scanf("%d", &a[i]);
 76     for(int i = 0; i<m; i++) {
 77         scanf("%d%d", &q[i].l, &q[i].r);
 78         q[i].id = i;
 79     }
 80     sort(q, q+m);
 81     int pos = 0;
 82     mem2(minn);
 83     for(int i = 1; i<=n; i++) {
 84         if(mp[a[i]]) {
 85             update(mp[a[i]], i-mp[a[i]], 1, n, 1);
 86         }
 87         mp[a[i]] = i;
 88         while(i == q[pos].r) {
 89             ans = inf;
 90             query(q[pos].l, i, 1, n, 1);
 91             if(ans == inf)
 92                 ans = -1;
 93             ans1[q[pos].id] = ans;
 94             pos++;
 95         }
 96     }
 97     for(int i = 0; i<m; i++)
 98         cout<<ans1[i]<<" ";
 99     return 0;
100 }