牛客小白月赛6 F发电（线段树）

版权声明： https://blog.csdn.net/Adusts/article/details/81835445

题目链接：https://www.nowcoder.com/acm/contest/136/F

线段树求区间的积。注意：点更新（除以一个数）的时候一定要乘以它的逆元否则一直WA。不要问我怎么知道的，，，

#include <cstdio>
#include <iostream>
#define lson l ,mid ,t << 1
#define rson mid + 1 ,r ,t << 1 | 1
#define MOD 1000000007
using namespace std;
typedef long long ll;
ll sum[50000*4+100];
ll inv(ll a) {
    if(a==1) return 1;
    return inv(MOD%a)*(MOD-MOD/a)%MOD;
}
void Pushup(int t) {
    sum[t] = ((sum[t<<1] % MOD) * (sum[t<<1|1] % MOD)) % MOD;
}
void BuidTree(ll l ,ll r ,ll t) {
    sum[t] = 1;
    if(l == r) {
        sum[t] %= MOD;
        return;
    }
    ll mid = (l + r) >> 1;
    BuidTree(lson);
    BuidTree(rson);
    Pushup(t);
}
void Update(ll l ,ll r ,ll t ,ll a ,ll b, ll flag) {
     if(l == r) {
        if(flag == 1) {
            sum[t] = (sum[t]*b)%MOD;   
        } else {
            sum[t] = (sum[t]*inv(b))%MOD;
        }
        return;
     }
     ll mid = (l + r) >> 1;
     if(a <= mid) Update(lson ,a ,b, flag);
     else Update(rson ,a ,b, flag);
     Pushup(t);
}
ll Query(ll l ,ll r ,ll t ,ll a ,ll b) {
    if(a <= l && b >= r)
    return sum[t];
    ll mid = (l + r) >> 1;
    ll ans = 1;
    if(a <= mid) ans = Query(lson ,a ,b) % MOD;
    if(b > mid) ans *= Query(rson ,a ,b) % MOD;
    return ans % MOD;
}
ll Scan() {   
    ll res = 0, flag = 0; 
    char ch; 
    if ((ch = getchar()) == '-') {  
        flag = 1; 
    }else if(ch >= '0' && ch <= '9') {
        res = ch - '0';
    }
    while ((ch = getchar()) >= '0' && ch <= '9'){
        res = res * 10 + (ch - '0'); 
    }
    return flag ? -res : res; 
} 
int main () {
    ll n, m, a, b, c;
    scanf("%lld %lld" ,&n, &m);
    BuidTree(1 ,n ,1);
    while(m--) {
       a = Scan();
       b = Scan();
       c = Scan();
       if(a == 1) {
           Update(1 ,n ,1 ,b ,c, a);
       } else if(a == 2) {
           Update(1 ,n ,1 ,b ,c, a);
       } else if(a == 3) {
           printf("%lld\n" ,Query(1 ,n ,1 ,b ,c) % MOD);
       }
    }
    return 0;
}