tyvj 1427 小白逛公园

对我这种弱菜来说挺难的，算是抄的代码吧

#include <set>#include <map>#include <ctime>#include <queue>#include <cmath>#include <stack>#include <limits>#include <vector>#include <bitset>#include <string>#include <cstdio>#include <cstring>#include <fstream>#include <string.h>#include <iostream>#include <algorithm>#define LL long long#define Vi vector<int>#define Si set<int>#define readf freopen("input.txt","r",stdin)#define writef freopen("output.txt","w",stdout)#define FF(i,a) for(int i(0); i < (a); i++)#define FD(i,a) for(int i(a); i >= (1); i--)#define FOR(i,a,b) for(int i(a);i <= (b); i++)#define FOD(i,a,b) for(int i(a);i >= (b); i--)#define PD(a) printf("%d\n",a)#define SET(a,b) memset(a,b,sizeof(a))#define SD(a) scanf("%d",&(a))#define LN printf("\n")#define PS printf(" ")#define pb push_back#define lson l , m , rt << 1#define rson m + 1 , r , rt << 1 | 1const double pi = acos(-1.0);const int maxn = 301;const int INF = ~0U>>1;const int dx[]={0,1,0,-1};const int dy[]={1,0,-1,0};using namespace std;int A[maxn];struct info{    int L,R,M,S;    info(int x=0):L(x),R(x),M(x),S(x){}}none;info operator+(const info&l,const info&r){    info f;    if(l.M==-INF)   return r;    if(r.M==-INF)   return l;    f.L=max(l.L,l.S+r.L);    f.R=max(r.R,r.S+l.R);    f.S=l.S+r.S;    f.M=max(l.M,r.M);    f.M=max(f.M,l.R+r.L);    return f;}info T[maxn*3];inline void Set(int t,int x){    T[t]=info(x);}void build(int t,int l,int r){    if(l+1==r){        Set(t,A[l]);        return;    }    build(t*2,l,(l+r)/2);    build(t*2+1,(l+r)/2,r);    T[t]=T[t*2]+T[t*2+1];}void change(int t,int l,int r,int p,int s){    if(l+1==r){        Set(t,s);return;    }    if(p<(l+r)/2) change(t*2,l,(l+r)/2,p,s);    else change(t*2+1,(l+r)/2,r,p,s);    T[t]=T[t*2]+T[t*2+1];}info ask(int t,int l,int r,int a,int b){    if(b<=l||a>=r) return none;    if(l>=a&&r<=b) return T[t];    return ask(t*2,l,(l+r)/2,a,b)+ask(t*2+1,(l+r)/2,r,a,b);}int main(){    none.M=-INF;    int n,m,a,b,c;    scanf("%d %d",&n,&m);    FF(i,n)scanf("%d",A+i);    build(1,0,n);    while(m--)    {        scanf("%d %d %d",&a,&b,&c);        if(a==1){            if(b>c) swap(b,c);            printf("%d\n",ask(1,0,n,b-1,c).M);        }        else change(1,0,n,b-1,c);    }}