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;    
}