CodeForces - 1440E Greedy Shopping

传送门：CodeForces - 1440E

思路分析

对于1操作来说，因为是对前缀进行修改，并不影响单调性，所以先二分找到第一个小于y的位置，然后区间修改
对于2操作直接在线段树上递归就行了

AC代码

#include <bits/stdc++.h>
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define fun function
#define sz(x) (x).size()
#define lowbit(x) (x)&(-x)
#define all(x) (x).begin(),(x).end()
#define mem(a,b) memset(a,b,sizeof(a))

namespace FastIO {
#define BUF_SIZE 100000
#define OUT_SIZE 100000
    bool IOerror=0;
    inline char nc() {
        static char buf[BUF_SIZE],*p1=buf+BUF_SIZE,*pend=buf+BUF_SIZE;
        if(p1==pend) {
            p1=buf;
            pend=buf+fread(buf,1,BUF_SIZE,stdin);
            if(pend==p1) {
                IOerror=1;
                return -1;
            }
        }
        return *p1++;
    }
    inline bool blank(char ch) {
        return ch==' '||ch=='\n'||ch=='\r'||ch=='\t';
    }
    template<class T> inline bool read(T &x) {
        bool sign=0;
        char ch=nc();
        x=0;
        for(; blank(ch); ch=nc());
        if(IOerror)return false;
        if(ch=='-')sign=1,ch=nc();
        for(; ch>='0'&&ch<='9'; ch=nc())x=x*10+ch-'0';
        if(sign)x=-x;
        return true;
    }
    template<class T,class... U>bool read(T& h,U&... t) {
        return read(h)&&read(t...);
    }
#undef OUT_SIZE
#undef BUF_SIZE
};
using namespace std;
using namespace FastIO;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define int long long
typedef long long ll;
typedef pair<int,int> pii;
typedef unsigned long long ull;

const int INF = 0x3f3f3f3f;
const int N = 2e5+10;

struct node {
    int l,r,mid,len,sum,mi,lazy;
} tree[N<<2];

int a[N];

#define ls x<<1
#define rs x<<1|1
void pp(int x) {
    tree[x].sum = tree[ls].sum+tree[rs].sum;
    tree[x].mi = min(tree[ls].mi,tree[rs].mi);
}

void build(int x,int l,int r) {
    tree[x] = {l,r,l+r>>1,r-l+1,0,0,0};
    if(l==r) {
        tree[x].sum = a[l];
        tree[x].mi = a[l];
        return ;
    }
    int mid = tree[x].mid;
    build(ls,l,mid);
    build(rs,mid+1,r);
    pp(x);
}

void update(int x,int lazy) {
    tree[x].lazy = lazy;
    tree[x].mi = lazy;
    tree[x].sum = lazy*tree[x].len;
}

void pd(int x) {
    if(tree[x].lazy) {
        int lazy = tree[x].lazy;
        update(ls,lazy);
        update(rs,lazy);
        tree[x].lazy = 0;
    }
}

void modify(int x,int l,int r,int k) {
    if(l<=tree[x].l && tree[x].r<=r ) {
        update(x,k);
        return ;
    }
    pd(x);
    int mid = tree[x].mid;
    if(l<=mid) modify(ls,l,r,k);
    if(r>mid) modify(rs,l,r,k);
    pp(x);
}

int find(int x,int val) {
    if(tree[x].l == tree[x].r) return tree[x].l;
    pd(x);
    if(tree[ls].mi<val) return find(ls,val);
    else return find(rs,val);
}

int query(int x,int l,int r,int &num) {
    if(tree[x].mi>num) return 0;
    if(l<=tree[x].l && tree[x].r<=r && tree[x].sum<=num) {
        num -= tree[x].sum;
        return tree[x].len;
    }
    pd(x);
    int mid = tree[x].mid;
    int ans = 0;
    if(l<=mid) ans+=query(ls,l,r,num);
    if(r>mid) ans+=query(rs,l,r,num);
    return ans;
}

signed main() {

#ifdef xiaofan
    freopen("1.in","r",stdin);
    freopen("1.out","w",stdout);
#endif

    int n,q;
    cin>>n>>q;
    for(int i=1; i<=n; i++) cin>>a[i];
    build(1,1,n);
    while(q--) {
        int op,x,y;
        cin>>op>>x>>y;
        if(op==1) {
            int pos = find(1,y);
            if(pos<=x) modify(1,pos,x,y);
        } else {
            cout<<query(1,x,n,y)<<endl;
        }
    }




    return 0;
}

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