hdu1754___I Hate It (线段树）

本文出自：svitter的blog ——尽管刷了很多水题，我依然在很浅的地方沉了

题意

算法

AC代码

//author: svtter
//

#include <iostream>
#include <stdio.h>
#include <string.h>
#include <vector>
#include <map>
#include <algorithm>
#include <queue>
#include <cmath>

#define INF 0xffffff
#define lln long long

#ifdef ONLINE_JUDGE
#define FOI(file) 0
#define FOW(file) 0
#else
#define FOI(file) freopen(file,"r",stdin);
#define FOW(file) freopen(file,"w",stdout);
#endif

using namespace std;

struct CNode
{
    int l, r;
    int max;
    int mid()
    {
        return (l+r)/2;
    }
};

CNode tree[600011];
void BuildTree(int root, int l, int r)
{
    tree[root].l = l;
    tree[root].r = r;
    tree[root].max = -INF;
    if(l != r)
    {
        BuildTree(root*2, l , (l+r)/2);
        BuildTree(root*2+1, (l+r)/2+1, r);
    }
}

void Insert(int root, int i, int v)
{
    if(tree[root].l == tree[root].r)
    {
        tree[root].max = v;
        return;
    }
    tree[root].max = max(tree[root].max, v);
    if(i <= tree[root].mid())
        Insert(root*2, i, v);
    else
        Insert(root*2+1, i, v);
}

int Query(int root, int l, int r)
{
    if(tree[root].l == l && tree[root].r == r)
        return tree[root].max;
    if(r <= tree[root].mid())
        return Query(root*2, l, r);
    else if(l > tree[root].mid())
        return Query(root*2+1, l, r);
    else
        return max(Query(root*2, l, tree[root].mid()),
            Query(root*2+1, tree[root].mid()+1, r));
}

int Update(int root, int i, int v)
{
    if(tree[root].l == tree[root].r)
        return tree[root].max = v;
    if(i <= tree[root].mid())
        return tree[root].max = max(Update(root*2, i, v), tree[root*2+1].max);
    else
        return tree[root].max = max(Update(root*2+1, i, v), tree[root*2].max);
}

int main()
{
    FOI("input");
    //FOW("output");
    //write your programme here

    int n, m, t;
    int i, j;
    int ans;
    char ch[10];
    while(~scanf("%d%d", &n, &m))
    {
        BuildTree(1,1,n);
        for(i = 1; i <= n; i++)
        {
            scanf("%d", &t);
            Insert(1, i, t);
        }
        for(i = 0; i < m ;i++)
        {
            scanf("%s", ch);
            if(ch[0] == 'U')
            {
                scanf("%d%d", &t, &j);
                Update(1, t, j);
            }
            else
            {
                scanf("%d%d", &t, &j);
                ans = Query(1, t, j );
                printf("%d\n", ans);
            }
        }
    }

    return 0;
}

hdu1754___I Hate It (线段树）