hdu 1754 不知道为什么老是runtime error ，数组已经开的够大了，哪位大神帮忙给看下啊
#include <stdio.h>

int max(int d,int b)
{
return d>b?d:b;
}


#define MAXN 2000000
int a[MAXN+5];


struct node
{
int left;
int right;
int sum;
} b[MAXN*2];


void build(int left , int right , int i)//为left，right ，sum赋值
{
int mid;
b[i].left=left;
b[i].right=right;
if(left==right)
{
b[i].sum=a[left];
return ;
}

mid=(left+right)/2;
build(left,mid,2*i);
build(mid+1,right,2*i+1);
b[i].sum=max(b[2*i].sum , b[2*i+1].sum);

}

void Update(int id,int value,int i)
{
if(b[i].left==b[i].right)
{
b[i].sum=value;
return ;
}


int mid =(b[i].left+b[i].right)/2;
if(mid>=id) Update(id,value,2*i);
if(id>mid) Update(id ,value,2*i+1);
b[i].sum=max(b[i*2].sum , b[2*i+1].sum);

}


int Query(int left, int right,int i)
{
int mid;
if(b[i].left==left && b[i].right ==right) return b[i].sum;
mid=(b[i].left+b[i].right)/2;
if(right<=mid) return Query(left,right,2*i);
if (left>mid ) return Query(left,right,2*i+1);
if(left<=mid && mid<right)
return max(Query(left,mid,2*i) , Query(mid+1,right,2*i+1));
}


int main()
{
int n,m;
char c;
int id,value;
int i;
while(scanf("%d%d",&n,&m)!=EOF)
{
//scanf("%d%d",&n,&m);
for(i=1;i<=n;i++)
{
scanf("%d",&a[i]);
}
build(1,n,1);
for(i=0;i<m;i++)
{
scanf("%c",&c);
scanf("%d%d",&id,&value);
if(c=='U') Update(id,value,1);
if(c=='Q') printf("%d\n",Query(id,value,1));
}
}
return 0;
}


[解决办法]
如下可以AC,lz对着看下

C/C++ code

#include<stdio.h>#define MAXN 200005int max(int d,int b){  return d>b?d:b;}int a[MAXN+5];struct node{  int left;  int right;  int sum;} b[MAXN*4];void build(int left , int right , int i)//为left，right ，sum赋值{  int mid;  b[i].left=left;  b[i].right=right;  if(left==right)  {  b[i].sum=a[left];  return ;  }  mid=(left+right)/2;  build(left,mid,2*i);  build(mid+1,right,2*i+1);  b[i].sum=max(b[2*i].sum , b[2*i+1].sum);}void Update(int id,int value,int i){  if(b[i].left==b[i].right)  {  b[i].sum=value;  return ;  }  int mid =(b[i].left+b[i].right)/2;  if(mid>=id) Update(id,value,2*i);  if(id>mid) Update(id ,value,2*i+1);  b[i].sum=max(b[i*2].sum , b[2*i+1].sum);}int Query(int left, int right,int i){  int mid;  if(b[i].left==left && b[i].right ==right) return b[i].sum;  mid=(b[i].left+b[i].right)/2;  if(right<=mid) return Query(left,right,2*i);  if (left>mid ) return Query(left,right,2*i+1);  if(left<=mid && mid<right)  return max(Query(left,mid,2*i) , Query(mid+1,right,2*i+1));}int main(){  int n,m;  char c;  int id,value;  int i;  while(scanf("%d%d",&n,&m)!=EOF)  {  //scanf("%d%d",&n,&m);  for(i=1;i<=n;i++)  {  scanf("%d",&a[i]);  }  build(1,n,1);  char c[3];  for(i=0;i<m;i++)  {  scanf("%s",c);  scanf("%d%d",&id,&value);  if(c[0]=='U') Update(id,value,1);  if(c[0]=='Q') printf("%d\n",Query(id,value,1));  }  }  return 0;} 
 
[解决办法]
读入数据 char c[3]; scanf("%s",c); 不要写成 char c ; scanf("%c",&c); 否则会有回车符