最裸的线段树单点替换，区间查找最大值。

#include 
     
      #include 
      
       using namespace std;#define M ((L+R)>>1)#define lson rt<<1,L,M#define rson rt<<1|1,M+1,R#define root 1,1,N#define max(a,b) ((a>b)?a:b)const int maxn = 200001;int maxv[maxn << 2],ql,qr,tar,v,val[maxn];inline void pushup(int rt) {    maxv[rt] = max(maxv[rt<<1],maxv[rt<<1|1]);}void build(int rt,int L,int R) {    if(L == R) maxv[rt] = val[L];    else {        build(lson); build(rson);        pushup(rt);    }}void update(int rt,int L,int R) {    if(L == R) maxv[rt] = v;    else {        if(tar <= M) update(lson);        if(tar > M) update(rson);        pushup(rt);    }}int query(int rt,int L,int R) {    if(ql <= L && qr >= R) return maxv[rt];    int lv = -INT_MAX,rv = -INT_MAX;    if(ql <= M) lv = query(lson);    if(qr > M) rv = query(rson);    return max(lv,rv);}int main() {    int N,m;     char cmd;    while(~scanf("%d%d",&N,&m)) {        for(int i = 1;i <= N;i++) scanf("%d",val + i);        build(root);        for(int i = 1;i <= m;i++) {            scanf(" %c",&cmd);            if(cmd == 'Q') {                scanf("%d%d",&ql,&qr);                printf("%d\n",query(root));            } else {                scanf("%d%d",&tar,&v);                update(root);            }        }    }    return 0;}