HDU 2795 Billboard（线段树单点更新）

题意: h*w的木板, 放进一些1*L的物品, 求每次放的可以放的最上面的位置, 放了之后就占据相应的位置

思路: 维护1-h线段的线段树 每段长w 然后不断维护区间的最大值  查询的时候优先往左儿子(相当于向上)

          然后就是单点更新的裸题了

代码:

//
// Created by TaoSama on 2015-09-18
// Copyright (c) 2015 TaoSama. All rights reserved.
//
//#pragma comment(linker, "/STACK:1024000000,1024000000")
#include <algorithm>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <string>
#include <set>
#include <vector>

using namespace std;
#define pr(x) cout << #x << " = " << x << " "
#define prln(x) cout << #x << " = " << x << endl
const int N = 2e5 + 10, INF = 0x3f3f3f3f, MOD = 1e9 + 7;

int w, n, q;

#define root 1, n, 1
#define lson l, m, rt << 1
#define rson m + 1, r, rt << 1 | 1

int maxv[N << 2];

void push_up(int rt) {
maxv[rt] = max(maxv[rt << 1], maxv[rt << 1 | 1]);
}

void build(int l, int r, int rt) {
maxv[rt] = w;
if(l == r) return;
int m = l + r >> 1;
build(lson);
build(rson);
}

int query(int v, int l, int r, int rt) {
if(l == r) {
maxv[rt] -= v;
return l;
}
int m = l + r >> 1;
int ret = maxv[rt << 1] >= v ? query(v, lson) : query(v, rson);
push_up(rt);
return ret;
}

int main() {
#ifdef LOCAL
freopen("in.txt", "r", stdin);
// freopen("out.txt","w",stdout);
#endif
ios_base::sync_with_stdio(0);

while(scanf("%d%d%d", &n, &w, &q) == 3) {
if(n > q) n = q;
build(root);
while(q--) {
int x; scanf("%d", &x);
if(maxv[1] < x) puts("-1");
else printf("%d\n", query(x, root));
}
}
return 0;
}