线段树功能:update:单点更新 query:区间最值

#include 
     
      #define lson l, m, rt<<1#define rson m+1, r, rt<<1|1using namespace std;const int MAXN = 200008;int maxs[MAXN<<2];void build(int l, int r, int rt){    if(l == r)    {        scanf("%d", &maxs[rt]);        return;    }    int m = (l + r) >> 1;    build(lson);    build(rson);    maxs[rt] = max(maxs[rt<<1], maxs[rt<<1|1]);}int query(int L, int R, int l, int r, int rt){    if(L <= l && r <= R) return maxs[rt];    int ret = 0;    int m = (l + r) >> 1;    if(L <= m) ret = max(ret, query(L, R, lson));    if(R > m) ret = max(ret, query(L, R, rson));    return ret;}void updata(int p, int news, int l, int r, int rt){    if(l == r)    {        maxs[rt] = news;        return;    }    int m = (l + r) >> 1;    if(p <= m) updata(p, news, lson);    else updata(p, news, rson);    maxs[rt] = max(maxs[rt<<1], maxs[rt<<1|1]);}int main(){//    freopen("in.txt", "r", stdin);    int n,k;    while(~scanf("%d%d", &n, &k))    {        build(1, n, 1);        while(k--)        {            char s[5];            scanf("%s", s);            int a,b;            scanf("%d%d", &a, &b);            if(s[0] == 'Q') printf("%d\n", query(a, b, 1, n, 1));            else updata(a, b, 1, n, 1);        }    }    return 0;}