UVA 1232 - SKYLINE(线段树)

UVA 1232 - SKYLINE

题目链接

题意:按顺序建房，在一条线段上，每个房子一个高度，要求出每间房子建上去后的轮廓线

思路：线段树延迟更新，一个setv作为高度的懒标记，此外还要在开一个cover表示当前结点一下是否都为同一高度

代码：

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

#define lson(x) ((x<<1)+1)
#define rson(x) ((x<<1)+2)

const int N = 100005;

int t, n;

struct Node {
int l, r, h, setv;
bool cover;
Node() {}
Node(int l, int r) {
this->l = l; this->r = r;
h = 0; setv = 0; cover = true;
}
} node[4 * N];

void pushup(int x) {
node[x].cover = ((node[lson(x)].h == node[rson(x)].h) && node[lson(x)].cover && node[rson(x)].cover);
node[x].h = node[lson(x)].h;
}

void pushdown(int x) {
node[lson(x)].setv = max(node[lson(x)].setv, node[x].setv);
node[rson(x)].setv = max(node[rson(x)].setv, node[x].setv);
node[lson(x)].h = max(node[lson(x)].setv, node[lson(x)].h);
node[rson(x)].h = max(node[rson(x)].setv, node[rson(x)].h);
}

void build(int l, int r, int x = 0) {
node[x] = Node(l, r);
if (l == r) return;
int mid = (l + r) / 2;
build(l, mid, lson(x));
build(mid + 1, r, rson(x));
}

int query(int l, int r, int v, int x = 0) {
if (node[x].cover && node[x].h > v) return 0;
if (node[x].l >= l && node[x].r <= r && node[x].cover) {
node[x].setv = v;
node[x].h = v;
return node[x].r - node[x].l + 1;
}
int mid = (node[x].l + node[x].r) / 2;
int ans = 0;
pushdown(x);
if (l <= mid) ans += query(l, r, v, lson(x));
if (r > mid) ans += query(l, r, v, rson(x));
pushup(x);
return ans;
}

int main() {
scanf("%d", &t);
while (t--) {
scanf("%d", &n);
build(1, N - 1);
int l, r, h;
int ans = 0;
while (n--) {
scanf("%d%d%d", &l, &r, &h);
ans += query(l, r - 1, h);
}
printf("%d\n", ans);
}
return 0;
}