URAL 1019 Line Painting

    可以用线段树进行区间染色、合并的操作。

    由于数据范围比较小，离散化后直接暴力更新也是可以的。

#include<stdio.h>

#include<string.h>

#include<stdlib.h>

#define MAXD 10010

int N, lc[4 * MAXD], rc[4 * MAXD], mc[4 * MAXD], to[4 * MAXD];

int M, tx[MAXD];

struct Seg

{

    int x, y;

    char b[5];     

}seg[MAXD];

int cmp(const void *_p, const void *_q)

{

    int *p = (int *)_p, *q = (int *)_q;

    return *p < *q ? -1 : 1;    

}

void build(int cur, int x, int y)

{

    int mid = (x + y) >> 1, ls = cur << 1, rs = (cur << 1) | 1;

    lc[cur] = rc[cur] = mc[cur] = tx[y + 1] - tx[x];

    to[cur] = -1;

    if(x == y)

        return ;

    build(ls, x, mid);

    build(rs, mid + 1, y);     

}

void init()

{

    int i, j, k;

    for(i = 0; i < N; i ++)

    {

        scanf("%d%d%s", &seg[i].x, &seg[i].y, seg[i].b);

        tx[i << 1] = seg[i].x, tx[(i << 1) | 1] = seg[i].y;

    }

    tx[i << 1] = 0, tx[(i << 1) | 1] = 1000000000;

    qsort(tx, (N + 1) << 1, sizeof(tx[0]), cmp);

    M = 0;

    for(i = 1; i < ((N + 1) << 1); i ++)

        if(tx[i] != tx[i - 1])

            tx[++ M] = tx[i];

    build(1, 0, M - 1);

}

void pushdown(int cur, int x, int y)

{

    int mid = (x + y) >> 1, ls = cur << 1, rs = (cur << 1) | 1;

    if(to[cur] != -1)

    {

        to[ls] = to[rs] = to[cur];

        mc[ls] = lc[ls] = rc[ls] = (to[cur] ? 0 : tx[mid + 1] - tx[x]);

        mc[rs] = lc[rs] = rc[rs] = (to[cur] ? 0 : tx[y + 1] - tx[mid + 1]);

        to[cur] = -1;

    }    

}

int Max(int x, int y)

{

    return x > y ? x : y;    

}

void update(int cur, int x, int y)

{

    int mid = (x + y) >> 1, ls = cur << 1, rs = (cur << 1) | 1;    

    mc[cur] = Max(mc[ls], mc[rs]);

    mc[cur] = Max(mc[cur], rc[ls] + lc[rs]);

    lc[cur] = lc[ls] + (lc[ls] == tx[mid + 1] - tx[x] ? lc[rs] : 0);

    rc[cur] = rc[rs] + (rc[rs] == tx[y + 1] - tx[mid + 1] ? rc[ls] : 0);

}

int BS(int x)

{

    int mid, min = 0, max = M + 1;

    for(;;)

    {

        mid = (min + max) >> 1;

        if(mid == min)

            break;

        if(tx[mid] <= x)

            min = mid;

        else

            max = mid;    

    }    

    return mid;

}

void color(int cur, int x, int y, int s, int t, int c)

{

    int mid = (x + y) >> 1, ls = cur << 1, rs = (cur << 1) | 1;

    if(x >= s && y <= t)

    {

        to[cur] = c;

        mc[cur] = lc[cur]    = rc[cur] = (c ? 0 : tx[y + 1] - tx[x]);

        return ;

    }    

    pushdown(cur, x, y);

    if(mid >= s)

        color(ls, x, mid, s, t, c);

    if(mid + 1 <= t)

        color(rs, mid + 1, y, s, t, c);

    update(cur, x, y);

}

void Search(int cur, int x, int y, int &s, int &t)

{

    int mid = (x + y) >> 1, ls = cur << 1, rs = (cur << 1) | 1;

    if(x == y)

    {

        s = tx[x], t = tx[y + 1];

        return ;

    }

    pushdown(cur, x, y);

    if(mc[ls] == mc[cur])

        Search(ls, x, mid, s, t);

    else if(rc[ls] + lc[rs] == mc[cur])

        s = tx[mid + 1] - rc[ls], t = tx[mid + 1] + lc[rs];

    else

        Search(rs, mid + 1, y, s, t);

}

void solve()

{

    int i, j, k;

    for(i = 0; i < N; i ++)

    {

        j = BS(seg[i].x), k = BS(seg[i].y);

        if(j < k)

        {

            if(seg[i].b[0] == 'b')

                color(1, 0, M - 1, j, k - 1, 1);

            else

                color(1, 0, M - 1, j, k - 1, 0);

        }

    }

    Search(1, 0, M - 1, j, k);

    printf("%d %d\n", j, k);

}

int main()

{

    while(scanf("%d", &N) == 1)

    {

        init();

        solve();

    }

    return 0;    

}