CodeForces - 1400E Clear the Multiset

传送门：CodeForces - 1400E

思路分析

对一次区间又两种操作，要么全部1操作，要么选一个最小值进行2操作，分治解决

AC代码

#include <bits/stdc++.h>
#define fi first
#define se second
#define ll long long
#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());

const int INF = 0x3f3f3f3f;
const int N = 1e4+10;

int a[N];

int solve(int l,int r){
    if(l>r) return 0;
    if(l==r) return a[l]==0?0:1;
    int mi=INF,pos;
    for(int i=l;i<=r;i++){
        if(a[i]<mi){
            mi = a[i];
            pos = i;
        }
    }
    for(int i=l;i<=r;i++) a[i]-=mi;
    int ans = min(r-l+1,solve(l,pos-1)+solve(pos+1,r)+mi);
    for(int i=l;i<=r;i++) a[i]+=mi;
    return ans;
} 

int main() {

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

    int n;
    cin>>n;
    for(int i=1;i<=n;i++) cin>>a[i];
    cout<<solve(1,n)<<endl;


    return 0;
}