题意：
已知(n)个数字，进行以下操作：
- (1.)区间([L,R]) 赋值为(x)
- (2.)区间([L,R]) 赋值为(max(a[i] + x, 0))
- (3.)区间([L,R]) 询问(0)个数
已知初始值(geq 0)，(xgeq0)。
思路：
吉司机线段树。
操作(1)可以直接打覆盖标记。
操作(2)可以分为两步：区间加(x)，然后取区间(max(a[i],0))。
操作(3)只要维护最小值的个数，因为不管怎么操作最后的值都(geq0)，然后查询的时候判最小值是不是(0)。
注意覆盖的时候，要把次小值初始化为(INF)。
代码：
#include<map>
#include<set>
#include<queue>
#include<cmath>
#include<stack>
#include<ctime>
#include<vector>
#include<cstdio>
#include<string>
#include<cstring>
#include<sstream>
#include<iostream>
#include<algorithm>
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
const int maxn = 5e5 + 5;
const int MAXM = 3e6;
const ll MOD = 998244353;
const ull seed = 131;
const ll INF = 1e16;
#define lson (rt << 1)
#define rson (rt << 1 | 1)
int a[maxn];
ll Min[maxn << 2], sMin[maxn << 2], add[maxn << 2], cov[maxn << 2];
int Minlen[maxn << 2];
inline void pushup(int rt){
if(Min[lson] > Min[rson]){
Min[rt] = Min[rson];
Minlen[rt] = Minlen[rson];
sMin[rt] = min(sMin[rson], Min[lson]);
}
if(Min[lson] < Min[rson]){
Min[rt] = Min[lson];
Minlen[rt] = Minlen[lson];
sMin[rt] = min(sMin[lson], Min[rson]);
}
if(Min[lson] == Min[rson]){
Min[rt] = Min[lson];
Minlen[rt] = Minlen[lson] + Minlen[rson];
sMin[rt] = min(sMin[lson], sMin[rson]);
}
}
inline void pushdown(int rt, int l, int r){
int m = (l + r) >> 1;
if(cov[rt] != -1){
Min[lson] = Min[rson] = cov[rt];
sMin[lson] = sMin[rson] = INF; //careful！！！！
cov[lson] = cov[rson] = cov[rt];
add[lson] = add[rson] = 0;
Minlen[lson] = m - l + 1;
Minlen[rson] = r - m;
cov[rt] = -1;
}
if(add[rt]){
Min[lson] += add[rt], sMin[lson] += add[rt];
Min[rson] += add[rt], sMin[rson] += add[rt];
add[lson] += add[rt], add[rson] += add[rt];
add[rt] = 0;
}
if(Min[lson] < Min[rt]){
if(sMin[lson] == Min[lson]) sMin[lson] = Min[rt];
Min[lson] = Min[rt];
}
if(Min[rson] < Min[rt]){
if(sMin[rson] == Min[rson]) sMin[rson] = Min[rt];
Min[rson] = Min[rt];
}
}
void build(int l, int r, int rt){
cov[rt] = -1, add[rt] = 0;
if(l == r){
Min[rt] = a[l];
sMin[rt] = INF;
Minlen[rt] = 1;
return;
}
int m = (l + r) >> 1;
build(l, m, lson);
build(m + 1, r, rson);
pushup(rt);
}
void cover(int L, int R, int l, int r, ll v, int rt){
if(L <= l && R >= r){
cov[rt] = v;
add[rt] = 0;
Min[rt] = v;
sMin[rt] = INF; //careful！！！！
Minlen[rt] = r - l + 1;
return;
}
pushdown(rt, l, r);
int m = (l + r) >> 1;
if(L <= m)
cover(L, R, l, m, v, lson);
if(R > m)
cover(L, R, m + 1, r, v, rson);
pushup(rt);
}
void update(int L, int R, int l, int r, ll v, int rt){
if(L <= l && R >= r){
Min[rt] += v;
sMin[rt] += v;
add[rt] += v;
return;
}
pushdown(rt, l, r);
int m = (l + r) >> 1;
if(L <= m)
update(L, R, l, m, v, lson);
if(R > m)
update(L, R, m + 1, r, v, rson);
pushup(rt);
}
void Less(int L, int R, int l, int r, ll v, int rt){
if(Min[rt] >= v) return;
if(L <= l && R >= r && sMin[rt] > v){ //>保证Minlen不变
Min[rt] = v;
return;
}
pushdown(rt, l, r);
int m = (l + r) >> 1;
if(L <= m)
Less(L, R, l, m, v, lson);
if(R > m)
Less(L, R, m + 1, r, v, rson);
pushup(rt);
}
int querySum(int L, int R, int l, int r, int rt){
if(L <= l && R >= r){
return Min[rt] == 0? Minlen[rt] : 0;
}
pushdown(rt, l, r);
int m = (l + r) >> 1;
int ret = 0;
if(L <= m)
ret += querySum(L, R, l, m, lson);
if(R > m)
ret += querySum(L, R, m + 1, r, rson);
return ret;
}
inline bool read(int &num){
char in;
bool IsN=false;
in = getchar();
if(in == EOF) return false;
while(in != '-' && (in < '0' || in > '9')) in = getchar();
if(in == '-'){ IsN = true; num = 0;}
else num = in - '0';
while(in = getchar(),in >= '0' && in <= '9'){
num *= 10, num += in-'0';
}
if(IsN) num = -num;
return true;
}
int main(){
int n, m;
read(n), read(m);
for(int i = 1; i <= n; i++) read(a[i]);
build(1, n, 1);
while(m--){
int l, r, x, op;
read(op), read(l), read(r);
if(op < 3) read(x);
if(op == 1) cover(l, r, 1, n, x, 1);
else if(op == 2) update(l, r, 1, n, x, 1), Less(l, r, 1, n, 0, 1);
else printf("%d
", querySum(l, r, 1, n, 1));
}
return 0;
}