最高分是多少

已知ID号和成绩，输入Q  A  B表示查询A+1到B之间最高分，输入U A B]表示将A+1同学的分数修改为B

#include <iostream>using namespace std;int main(){int grade[30000] = {0};int i = 0;int j = 0;int stu_num = 0;int op_num = 0;char op;   //存储操作符int from = 0;int to = 0;int max_grade = -1;cin>>stu_num;cin>>op_num;for(i = 0; i < stu_num; ++i)  {cin>>grade[i];}for(i = 0; i < op_num; ++i){max_grade = -1;cin>>op;cin>>from;cin>>to;if(op == 'Q'){max_grade = grade[from];for(j = from; j < to; ++j){if(grade[j] > max_grade){max_grade = grade[j];}}cout<<max_grade<<endl;}else if(op == 'U'){grade[from] = to;}}return 0;}