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  • Sereja and Suffixes(思维)

    Sereja and Suffixes
    Time Limit:1000MS     Memory Limit:262144KB     64bit IO Format:%I64d & %I64u

    Description

    Sereja has an array a, consisting of n integers a1, a2, ..., an. The boy cannot sit and do nothing, he decided to study an array. Sereja took a piece of paper and wrote out m integers l1, l2, ..., lm(1 ≤ li ≤ n). For each number li he wants to know how many distinct numbers are staying on the positions li, li + 1, ..., n. Formally, he want to find the number of distinct numbers among ali, ali + 1, ..., an.?

    Sereja wrote out the necessary array elements but the array was so large and the boy was so pressed for time. Help him, find the answer for the described question for each li.

    Input

    The first line contains two integers n and m(1 ≤ n, m ≤ 105). The second line contains n integers a1, a2, ..., an(1 ≤ ai ≤ 105) — the array elements.

    Next m lines contain integers l1, l2, ..., lm. The i-th line contains integer li(1 ≤ li ≤ n).

    Output

    Print m lines — on the i-th line print the answer to the number li.

    Sample Input

    Input
    10 10 1 2 3 4 1 2 3 4 100000 99999 1 2 3 4 5 6 7 8 9 10
    Output
    6 6 6 6 6 5 4 3 2 1
    题解:让求x到n的不同数字的个数;打表,对于m次询问,如果每次都暴力肯定超了,由于n是固定的,所以打下表,从后往前;
    代码:
    #include<iostream>
    #include<cstdio>
    #include<cstring>
    #include<cmath>
    #include<algorithm>
    #include<set>
    #include<map>
    using namespace std;
    const int MAXN = 1e5+100;
    class Ary{
        public:
            int n,m;
            int a[MAXN];
            int dp[MAXN];
            set<int>st;
            Ary(int n,int m):n(n),m(m){
                for(int i = 1; i <= n; i++){
                    cin >> a[i];
                }
            }
            int work(){
                int cnt = 0;
                for(int i = n; i >= 1; i--){
                    if(!st.count(a[i])){
                        cnt++;
                        st.insert(a[i]);
                    }
                    dp[i] = cnt;
                }
                //cout << endl;
            }
            ~Ary(){
                //cout << "对象毁灭" << endl;
            }
    };
    int main(){
        int n,m;
        while(~scanf("%d%d", &n, &m)){
            Ary boy(n,m);
            int temp;
            boy.work();
            while(m--){
                scanf("%d",&temp);
                printf("%d
    ",boy.dp[temp]);
            }
        }
        return 0;
    }
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  • 原文地址:https://www.cnblogs.com/handsomecui/p/5343909.html
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