1 #include <iostream> 2 #include <cstdio> 3 #include <cstring> 4 #include <queue> 5 #include <cstdlib> 6 #include <algorithm> 7 const int maxn = 200000+10; 8 using namespace std; 9 int a[maxn], n, m;10 struct line11 {12     int l, r, val;  //val代表该区间的最大值13 }tr[4*maxn];14 15 void build(int o, int l, int r)16 {17     tr[o].l = l; tr[o].r = r;18     if(l==r)19     {20         tr[o].val = a[l];21         return;22     }23     int mid = (l+r)/2;24     build(2*o, l, mid);25     build(2*o+1, mid+1, r);26     tr[o].val = max(tr[2*o].val, tr[2*o+1].val);27 }28 int query(int o, int l, int r)29 {30     if(tr[o].l==l && tr[o].r==r)31         return tr[o].val;32     int mid = (tr[o].l+tr[o].r)/2;33     if(r<=mid) query(2*o, l, r);  //这里一定记住只要不跨区间就是l，r。因为这个错了几次34     else if(l > mid) query(2*o+1, l, r);35     else36     {37         return max(query(2*o, l, mid), query(2*o+1, mid+1, r));38     }39 }40 void update(int o, int p, int v)41 {42     if(tr[o].l==tr[o].r && tr[o].l==p)43     {44         tr[o].val = v;45         return;46     }47     int mid = (tr[o].l + tr[o].r)/2;48     if(p<=mid) update(2*o, p, v);49     else update(2*o+1, p, v);50     tr[o].val = max(tr[2*o].val, tr[2*o+1].val);51 }52 int main()53 {54     char ch;55     int i, l, r;56     while(~scanf("%d%d", &n, &m))57     {58         for(i = 1; i <= n; i++)59         scanf("%d", &a[i]);60         build(1, 1, n);61 62         for(i = 0; i < m; i++)63         {64             getchar();65             scanf("%c%d%d", &ch, &l, &r);66             if(ch==‘Q‘)67                printf("%d\n", query(1, l, r));68             else69                update(1, l, r);70         }71     }72     return 0;73 }