HDU 1754 I Hate It

/*
线段树
更新节点,区间最值
*/
#include <stdio.h> 
#include <stdlib.h>
const int MAXN = 200001;
int MAX(int x, int y){
    return x > y ? x : y;
}
struct segTree{
    int L,R;
    int max;
};
segTree tree[MAXN << 2];
int st[MAXN];
void bulid(int left,int right, int t){
    tree[t].L = left;
    tree[t].R = right;
    if( left == right )
        tree[t].max = st[left];
    else {
        int mid = ( left + right ) >> 1;
        bulid(left, mid, 2 * t);
        bulid(mid + 1, right, 2 * t + 1);
        tree[t].max = MAX(tree[2 * t].max, tree[2 * t + 1].max);
    }
}
void updata(int num, int score, int t){
    if(tree[t].L == num && tree[t].R == num){
        tree[t].max = score;
    } else if(tree[t].L < tree[t].R ){
        int mid = (tree[t].L + tree[t].R) >> 1;
        if(num > mid){
            updata(num, score, 2 * t + 1);
        }
        if(num <= mid){
            updata(num, score, 2 * t);
        }
        tree[t].max = MAX(tree[2 * t].max, tree[2 * t + 1].max);
    }
}
int query(int left, int right, int t){
    if (left == tree[t].L && right == tree[t].R ){
        return tree[t].max;
    } else if(tree[t].L < tree[t].R ){
        int mid = (tree[t].L + tree[t].R ) >> 1;
        if ( right <= mid ){
            return query(left, right, t * 2);
        } else if ( left > mid ){
            return query(left, right, t * 2 + 1);
        } else {
            return MAX(query(left, mid, t * 2), query(mid + 1, right, t * 2 + 1));
        }
    }
    return 0;
}
int main(){
//    freopen("1012.txt","r",stdin);
    int n, m, a, b;
    char C;
    while (scanf("%d%d",&n, &m) != EOF){
        for(int i = 1; i <= n; i++)
            scanf("%d",&st[i]);
        bulid(1,n,1);
        getchar();    //这里错  
        while(m--){
                    scanf("%c",&C);
                    if(C=='Q'){
                        scanf("%d%d",&a,&b);
                          printf("%d\n",query(a,b,1));
                    } else {
                        scanf("%d%d",&a,&b);
                        updata(a,b,1);
                    }
                    getchar();
            }
    }
    return 0;            
}