POJ 3667 Hotel(算竞进阶习题)

线段树区间染色

题目要求最大的连续段的左端点，我们在查询的时候返回最左端即可，注意查找顺序，应该从左到右！！

另外这类染色的push_down其实比较简单，直接染成上一层的标记即可

push_up和连续子段和有点像，需要维护前缀和后缀

#include <bits/stdc++.h>
#define INF 0x3f3f3f3f
using namespace std;
typedef long long ll;
inline int lowbit(int x){ return x & (-x); }
inline int read(){
    int X = 0, w = 0; char ch = 0;
    while(!isdigit(ch)) { w |= ch == '-'; ch = getchar(); }
    while(isdigit(ch)) X = (X << 3) + (X << 1) + (ch ^ 48), ch = getchar();
    return w ? -X : X;
}
inline int gcd(int a, int b){ return a % b ? gcd(b, a % b) : b; }
inline int lcm(int a, int b){ return a / gcd(a, b) * b; }
template<typename T>
inline T max(T x, T y, T z){ return max(max(x, y), z); }
template<typename T>
inline T min(T x, T y, T z){ return min(min(x, y), z); }
template<typename A, typename B, typename C>
inline A fpow(A x, B p, C yql){
    A ans = 1;
    for(; p; p >>= 1, x = 1LL * x * x % yql)if(p & 1)ans = 1LL * x * ans % yql;
    return ans;
}
const int N = 50005;
int n, m;
int prefix[N<<2], suffix[N<<2], tree[N<<2], lazy[N<<2];

void push_up(int rt, int l, int r){
    int lson = rt << 1, rson = rt << 1 | 1;
    int mid = (l + r) >> 1;
    tree[rt] = max(tree[lson], tree[rson], suffix[lson] + prefix[rson]);
    prefix[rt] = prefix[lson], suffix[rt] = suffix[rson];
    if(tree[lson] == mid - l + 1) prefix[rt] += prefix[rson];
    if(tree[rson] == r - mid) suffix[rt] += suffix[lson];
}

void push_down(int rt, int l, int r){
    if(lazy[rt] != -1){
        int lson = rt << 1, rson = rt << 1 | 1;
        int mid = (l + r) >> 1;
        lazy[lson] = lazy[rson] = lazy[rt];
        prefix[lson] = suffix[lson] = tree[lson] = lazy[rt] * (mid - l + 1);
        prefix[rson] = suffix[rson] = tree[rson] = lazy[rt] * (r - mid);
        lazy[rt] = -1;
    }
}

void buildTree(int rt, int l, int r){
    if(l == r){
        prefix[rt] = suffix[rt] = tree[rt] = 1;
        lazy[rt] = -1;
        return;
    }
    lazy[rt] = -1;
    int mid = (l + r) >> 1;
    buildTree(rt << 1, l, mid);
    buildTree(rt << 1 | 1, mid + 1, r);
    push_up(rt, l, r);
}

void modify(int rt, int l, int r, int modifyL, int modifyR, int status){
    if(l == modifyL && r == modifyR){
        tree[rt] = prefix[rt] = suffix[rt] = (r - l + 1) * status;
        lazy[rt] = status;
        return;
    }
    push_down(rt, l, r);
    int mid = (l + r) >> 1;
    if(modifyL > mid) modify(rt << 1 | 1, mid + 1, r, modifyL, modifyR, status);
    else if(modifyR <= mid) modify(rt << 1, l, mid, modifyL, modifyR, status);
    else{
        modify(rt << 1, l, mid, modifyL, mid, status);
        modify(rt << 1 | 1, mid + 1, r, mid + 1, modifyR, status);
    }
    push_up(rt, l, r);
}

int query(int rt, int l, int r, int len){
    if(prefix[rt] >= len) return l;
    push_down(rt, l, r);
    int mid = (l + r) >> 1, lson = rt << 1, rson = rt << 1 | 1;
    if(tree[lson] >= len) return query(lson, l, mid, len);
    //else if(tree[rson] >= len) return query(rson, mid + 1, r, len);
    else if(suffix[lson] + prefix[rson] >= len) return mid - suffix[lson] + 1;
    else if(tree[rson] >= len) return query(rson, mid + 1, r, len);
    else return 0;
}

int main(){

    n = read(), m = read();
    buildTree(1, 1, n);
    while(m --){
        int opt = read();
        if(opt == 1){
            int len = read();
            int pos = query(1, 1, n, len);
            if(pos != 0 ) modify(1, 1, n, pos, pos + len - 1, 0);
            printf("%d
", pos);
        }
        else if(opt == 2){
            int x = read(), y = read();
            modify(1, 1, n, x, x + y - 1, 1);
        }
    }
    return 0;
}