# quhengyi11 的博客

### 题解 P1442 【铁球落地】

posted on 2018-11-01 19:44:05 | under 线段树 |

╮(╯_╰)╭一道码力题。对于我这种蒟蒻超级不友好

5 3

11 11

1 3 33

2 4 55

4 3 44

7 7 11

9 11 16

#include<bits/stdc++.h>
#define fo(i, a, b) for (Re int i = (a); i <= (b); ++i)
#define fd(i, a, b) for (Re int i = (a); i >= (b); --i)
#define edge(i, u) for (Re int i = head[u], v = e[i].v; i; i = e[i].nxt, v = e[i].v)
#define N 200005
#define Re register
#define pb push_back
#define F first
#define S second
#define ll long long
#define inf 1000000007
#define mp std::make_pair
#define lowbit(x) (x & -x)
#define ls (k << 1)
#define rs (k << 1 | 1)
#define mod 1000000007
int n, T, X, Y, a[N], tot, cnt, ans, x, y, w, i, pos, now, dp[N][2], L, R, m, X0, Y0;
struct line{
int x1, x2, y, l, r;
friend bool operator < (line qwq, line qaq)
{
return qaq.y < qwq.y;
}
}p[N];
struct tree{
int v;
bool flag;
}t[N << 2];
inline void pushdown (int k)
{
if (t[k].flag)
{
t[k].flag = 0;
t[ls].v = t[rs].v = t[k].v;
t[rs].flag = t[ls].flag = 1;
}
}
inline void add (int k, int l, int r)
{
if (L <= l && R >= r)
{
t[k].v = i;
t[k].flag = 1;
return;
}
pushdown(k);
int mid = l + r >> 1;
if (L <= mid) add(ls, l, mid);
if (mid < R) add(rs, mid + 1, r);
}
inline int query (int k, int l, int r)
{
if (t[k].flag && l <= now && now <= r || l == r && l == now)
{
return t[k].v;
}
pushdown(k);
int mid = l + r >> 1;
if (now <= mid) return query(ls, l, mid);
if (mid < now) return query(rs, mid + 1, r);
}
inline int abs (int x) {return x < 0 ? -x : x;}
inline int dis (int x1, int y1, int x2, int y2) {return abs(x1 - x2) + abs(y1 - y2);}
int main ()
{
scanf("%d %d", &n, &m);
scanf("%d %d", &X0, &Y0);
fo (i, 1, n)
{
scanf("%d %d %d", &p[i].y, &p[i].x1, &p[i].x2);
a[i] = p[i].x1;
a[i + n] = p[i].x2;
}
std::sort(a + 1, a + n + n + 1);
cnt = std::unique(a + 1, a + n + n + 1) - a - 1;
std::sort(p + 1, p + n + 1);//y值从高到低
fo (i, 1, n)
if (p[i].y <= Y0 && p[i].x1 <= X0 && p[i].x2 >= X0)
{
pos = i;
break;
}
int j;
i = 0;
L = 1; R = cnt;
add(1, 1, cnt);
for (i = n; i; --i)
{
now = std::lower_bound(a + 1, a + cnt + 1, p[i].x1) - a;
j = query(1, 1, cnt);
if (p[i].y - p[j].y <= m) p[i].l = j; else p[i].l = -1;
now = std::lower_bound(a + 1, a + cnt + 1, p[i].x2) - a;
j = query(1, 1, cnt);
if (p[i].y - p[j].y <= m) p[i].r = j; else p[i].r = -1;
L = std::lower_bound(a + 1, a + cnt + 1, p[i].x1) - a;
R = std::lower_bound(a + 1, a + cnt + 1, p[i].x2) - a;
add(1, 1, cnt);
}
memset(dp, 0x3f, sizeof dp);
//    fo (i, 1, n)
//        printf("i = %d l = %d r = %d\n", i, p[i].l, p[i].r);
dp[pos][0] = dis(X0, Y0, p[pos].x1, p[pos].y);
dp[pos][1] = dis(X0, Y0, p[pos].x2, p[pos].y);
fo (i, 1, n)
{
int nxt = p[i].l;
if (nxt != -1)
{
if (!nxt)
dp[0][0] = std::min(dp[0][0], dp[i][0] + p[i].y);
else
{
dp[nxt][0] = std::min(dp[nxt][0], dp[i][0] + dis(p[i].x1, p[i].y, p[nxt].x1, p[nxt].y));
dp[nxt][1] = std::min(dp[nxt][1], dp[i][0] + dis(p[i].x1, p[i].y, p[nxt].x2, p[nxt].y));
}
}
nxt = p[i].r;
if (nxt != -1)
{
if (!nxt)
dp[0][0] = std::min(dp[0][0], dp[i][1] + p[i].y);
else
{
dp[nxt][0] = std::min(dp[nxt][0], dp[i][1] + dis(p[i].x2, p[i].y, p[nxt].x1, p[nxt].y));
dp[nxt][1] = std::min(dp[nxt][1], dp[i][1] + dis(p[i].x2, p[i].y, p[nxt].x2, p[nxt].y));
}
}
}
printf("%d\n", dp[0][0]);
return 0;
}