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  • [POI 2014] Little Bird

    [题目链接]

             https://www.lydsy.com/JudgeOnline/problem.php?id=3831

    [算法]

            单调队列优化动态规划

            时间复杂度 : O(N)

    [代码]

              

    #include<bits/stdc++.h>
    using namespace std;
    #define MAXN 1000010
    const int inf = 2e9;
    
    int n;
    int a[MAXN] , f[MAXN];
    
    template <typename T> inline void chkmax(T &x,T y) { x = max(x,y); }
    template <typename T> inline void chkmin(T &x,T y) { x = min(x,y); }
    template <typename T> inline void read(T &x)
    {
        T f = 1; x = 0;
        char c = getchar();
        for (; !isdigit(c); c = getchar()) if (c == '-') f = -f;
        for (; isdigit(c); c = getchar()) x = (x << 3) + (x << 1) + c - '0';
        x *= f;
    }
    inline int solve(int k)
    {
            deque< int > q;
            for (int i = 1; i <= n; i++) f[i] = inf;
            q.clear();
            for (int i = 1; i <= n; i++)
            {
                    while (!q.empty() && i - q.front() > k) q.pop_front();
                    if (q.empty()) f[i] = 0;
                    else f[i] = f[q.front()] + (a[q.front()] <= a[i]);
                    while (!q.empty() && ((f[i] < f[q.back()]) || ((f[i] == f[q.back()]) && a[i] >= a[q.back()]))) q.pop_back();
                    q.push_back(i);
            }        
            return f[n];
    }
    
    int main()
    {
            
            read(n);
            for (int i = 1; i <= n; i++) read(a[i]);
            int T;
            read(T);
            while (T--)
            {
                    int x;
                    read(x);
                    printf("%d
    " , solve(x));
            }
            
            return 0;
        
    }
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  • 原文地址:https://www.cnblogs.com/evenbao/p/9911902.html
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