hdu1754I Hate It

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>
#include <queue>
using namespace std;
const int maxn = 201000;
int value[maxn*3];//value[maxn*2] -> WA
int maxv[maxn*3];//total of the segment.
//Accepted	1754	2078MS	6556K	2308 B	G++	Achiberx
//Accepted	1754	1015MS	6504K	1955 B	C++	Achiberx
int n, m;
int ql, qr;//全局变量。
//ql, qr /给出的查询区间。

int update(int o, int L, int R, int v) {
    if(L == R && L ==ql ) {
        maxv[o] = v;
        return v;
    }
    int M = L + (R-L)/2;
    if(ql <= M) {//单点修改，在左右选择一个。
       update(o*2, L, M, v);
    }
    else {
       update(o*2+1, M+1, R, v);
    }
    maxv[o] = max(maxv[o*2], maxv[o*2+1]);
    return maxv[o];
}

int query(int o, int L, int R) {
    if(ql <= L && R <= qr) return maxv[o];
    int ans = 0;
    int M = L + (R-L)/2;
    if(ql <= M) {
        ans = max(ans, query(o*2, L, M));
    }
    if(qr > M) {
        ans = max(ans, query(o*2+1, M+1, R));
    }
    return ans;
}

void init() {
    for(int i = 1; i <= n; i++) {
        ql = i;
        update(1, 1, n, value[i]);
    }
}

int main()
{
    int a, b;
    while(scanf("%d%d", &n, &m) != EOF) {
        for(int i = 1; i <= n*2; i++) {
            value[i] = 0;
            maxv[i] = 0;
        }
        for(int i = 1; i <=n; i++) {
            scanf("%d", value+i);
        }
        init();
        for(int i = 0; i < m; i++) {
            char c[5];
            scanf("%s", c);
            scanf("%d%d",&a, &b);
            if(c[0]=='U') {
                ql = a;
                update(1, 1, n, b);
            }
            else if(c[0]=='Q') {
                ql = a; qr = b;
                int res = query(1, 1, n);
                printf("%d\n", res);
            }
        }
    }
    return 0;
}