51Nod-1593-公园晨跑

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ACM模版

描述

题解

十分有趣的一个问题，用到线段树了……

我学姐写这个题解十分的详细，我想我一定不会写的更详细，所以直接给大家一个我学姐的博客吧，可以去哪儿看一下题解……但是学姐的线段树写得真让人感觉不习惯，所以我自己只贴一下代码吧！

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代码

#include <stdio.h>#include <algorithm>#include <string.h>#define lson rt << 1#define rson rt << 1 | 1using namespace std;typedef long long ll;const int MAXN = 3e5 + 10;const ll INF = 0x3f3f3f3f3f3f3f3f;struct point{    int pos;    ll mx;    point()    {        mx = -INF;    }};struct Seg{    int root, pos, n;    ll mx, key;    point A[MAXN << 3];    Seg()    {        root = 1;    }    void push_up(point &a, int rt)    {        if (A[lson].mx > A[rson].mx)        {            a.mx = A[lson].mx;            a.pos = A[lson].pos;        }        else        {            a.mx = A[rson].mx;            a.pos = A[rson].pos;        }    }    void update(int x, int l, int r, int rt)    {        if (x > r || x < l)        {            return ;        }        if (l == r)        {            A[rt].mx = key;            A[rt].pos = x;            return ;        }        int m = (l + r) >> 1;        update(x, l, m, lson);        update(x, m + 1, r, rson);        push_up(A[rt], rt);    }    void update(int x, ll k)    {        key = k;        update(x, 0, n, root);    }    void query(int l, int r, int L, int R, int rt)    {        if (R < l || L > r)        {            return ;        }        if (L >= l && R <= r)        {            if (A[rt].mx > mx)            {                mx = A[rt].mx;                pos = A[rt].pos;            }            return ;        }        int M = (L + R) >> 1;        query(l, r, L, M, lson);        query(l, r, M + 1, R, rson);    }    int query(int l, int r)    {        mx = -INF;        query(l, r, 0, n, root);        return pos;    }} segA, segB;ll A[MAXN << 1];ll B[MAXN << 1];int n, m;ll h;template <class T>inline void scan_d(T &ret){    char c;    ret = 0;    while ((c = getchar()) < '0' || c > '9');    while (c >= '0' && c <= '9')    {        ret = ret * 10 + (c - '0'), c = getchar();    }}template <class T>inline void print_d(T x){    if (x > 9)    {        print_d(x / 10);    }    putchar(x % 10 + '0');}int main (){    scan_d(n), scan_d(m);    int len = n << 1;    for (int i = 1; i <= n; i++)    {        scan_d(A[i]);        A[i + n] = A[i];    }    for (int i = 1; i < len; i++)    {        A[i] += A[i - 1];    }    memcpy(B, A, sizeof(A));    for (int i = 0; i < n; i++)    {        scan_d(h);        h = h << 1;        A[i] += h;        B[i] -= h;        A[i + n] += h;        B[i + n] -= h;    }    segA.n = len - 1;    segB.n = len - 1;    for (int i = 0; i < len; i++)    {        segA.update(i, A[i]);        segB.update(i, -B[i]);    }    int l, r;    while (m--)    {        scan_d(l), scan_d(r);        l--;        r--;        if (l <= r)        {            int tmp = r + 1;            r = n + l - 1;            l = tmp;        }        else        {            swap(l, r);            l++;            r--;        }        int mx = segA.query(l, r);        int mn = segB.query(l, r);        if (mx == mn)        {            int tmp = -1, tmp_;            if (mx > l)            {                tmp = segA.query(l, mx - 1);            }            if (mx < r)            {                tmp_ = segA.query(mx + 1, r);                if (tmp == -1|| A[tmp] < A[tmp_])                {                    tmp = tmp_;                }            }            ll ans1 = A[tmp] - B[mn];            tmp = -1;            if (mn > l)            {                tmp = segB.query(l, mn - 1);            }            if (mn < r)            {                tmp_ = segB.query(mn + 1, r);                if (tmp == -1 || B[tmp] > B[tmp_])                {                    tmp = tmp_;                }            }            ll ans2 = A[mx] - B[tmp];            print_d(max(ans1, ans2));            putchar(10);        }        else        {            print_d(A[mx] - B[mn]);            putchar(10);        }    }    return 0;}

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