HDU1754-ZKW线段树

Posted 2020-10-27 Helica

单点更新，区间最值

 HDU 1754

//
// Created by helica on 2018/3/18.
//

//zkw线段树 单点修改 区间求最值
//HDU 1754

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>

using namespace std;
const int N = 200000 + 10;

int M = 1;
int T[N<<2];

void change(int x, int v){
    T[M+x] = v;
    for(int p= (M+x)>>1;p;p>>=1) T[p] = max(T[p<<1], T[p<<1|1]);
}

int query(int s, int t){
    int ans = -1;
    for (s=M+s-1,t=M+t+1; s^t^1; s>>=1, t>>=1) {
        if (~s&1) ans = max(ans, T[s^1]);
        if ( t&1) ans = max(ans, T[t^1]);
    }
    return ans;
}

int main(){
    int n,q,op,s,t;
    while(~scanf("%d %d", &n, &q)){
        memset(T, 0, sizeof T);

        for(M=1;M<n;M<<=1);
        for (int i=0,tmp;i<n;i++) {
            scanf("%d", &tmp);
            change(i+1, tmp);
        }

        for(int i=0;i<q;i++){
            char op[5];
            scanf("%s %d %d", op, &s, &t);
            if(op[0] == ‘U‘){
                change(s, t);
            }else if(op[0] == ‘Q‘){
                printf("%d\n", query(s, t));
            }
        }
    }
}