注意写代码的时候上下限要定的大一些,避免数据比较夸张,最好直接用long long进行运算
原题
#include
using namespace std;
#define int long long
const int N = 1e5 + 10;
const int INF = 0x3f3f3f3f3f;
int n, m;
struct Node{
int l, r;
int maxn;
}tr[N * 4];
int w[N];
void push_up(int u){
tr[u].maxn = max(tr[u << 1].maxn, tr[u << 1 | 1].maxn);
}
void build(int u, int l, int r){
//此时tr[]还没哟值,所以不能用于判断
if(l == r) tr[u] = {l, r, w[r]};
else{
tr[u] = {l, r};
int mid = l + r >> 1;
//建树的时候不用判断下一层的边界,直接建树即可
build(u << 1, l, mid);
build(u << 1 | 1, mid + 1, r);
push_up(u);
}
}
int query(int u, int l, int r){
if(l <= tr[u].l && r >= tr[u].r) return tr[u].maxn;
int res = -INF;
int mid = tr[u].l + tr[u].r >> 1;
if(l <= mid) res = max(res, query(u << 1, l, r));
if(r > mid) res = max(res, query(u << 1 | 1, l, r));
return res;
}
signed main()
{
scanf("%lld %lld", &n, &m);
for(int i = 1; i <= n; i ++ ){
scanf("%lld", &w[i]);
}
build(1, 1, n);
while(m -- ){
int a, b;
scanf("%lld%lld", &a, &b);
printf("%lld\n", query(1, a, b));
}
return 0;
}
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