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-8;
const int mod = 1e9+7;
const int inf = 1061109567;
const int dir[][2] = { {-1, 0}, {1, 0}, {0, -1}, {0, 1} };
const int maxn = 5e5+5;
int minn[maxn<<2], 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<<1], minn[rt<<1|1]);
}
void update(int p, int val, int l, int r, int rt) {
    if(l == r) {
        minn[rt] = val;
        return ;
    }
    int m = l+r>>1;
    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>>1;
    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 = 1; i<=n; i++)
        scanf("%d", &a[i]);
    for(int i = 0; i<m; i++) {
        scanf("%d%d", &q[i].l, &q[i].r);
        q[i].id = i;
    }
    sort(q, q+m);
    int pos = 0;
    mem2(minn);
    for(int i = 1; i<=n; i++) {
        if(mp[a[i]]) {
            update(mp[a[i]], i-mp[a[i]], 1, n, 1);
        }
        mp[a[i]] = i;
        while(i == q[pos].r) {
            ans = inf;
            query(q[pos].l, i, 1, n, 1);
            if(ans == inf)
                ans = -1;
            ans1[q[pos].id] = ans;
            pos++;
        }
    }
    for(int i = 0; i<m; i++)
        cout<<ans1[i]<<" ";
    return 0;
}