hdu1754 I Hate It

来源：互联网发布：三菱fx编程m代表什么编辑：程序博客网时间：2024/05/02 09:48

用线段树维护区间最大值，支持修改单点的值。

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;#define LL(x) (x<<1)#define RR(x) (x<<1|1)const int maxn = 200005;struct node {    int l, r;    int Max;}tree[maxn*4];int num[maxn];void build(int rt, int l, int r) {    tree[rt].l = l;    tree[rt].r = r;    if(tree[rt].l == tree[rt].r) {        tree[rt].Max = num[l];        return ;    }    int mid = (tree[rt].l + tree[rt].r)>>1;    build(LL(rt), l, mid);    build(RR(rt), mid+1, r);    tree[rt].Max = max(tree[LL(rt)].Max, tree[RR(rt)].Max);}void update(int rt, int pos, int val) {    if(tree[rt].l == tree[rt].r) {        tree[rt].Max = val;        return ;    }    int mid = (tree[rt].l + tree[rt].r)>>1;    if(pos <=mid) update(LL(rt), pos, val);    else update(RR(rt), pos, val);    tree[rt].Max = max(tree[LL(rt)].Max, tree[RR(rt)].Max);}int query(int rt, int l, int r) {    if(l <= tree[rt].l && r >= tree[rt].r) {        return tree[rt].Max;    }    int mid = (tree[rt].l + tree[rt].r)>>1;    int ret = 0;    if(l <= mid) ret =max(ret, query(LL(rt), l, r) );    if(r > mid ) ret =max(ret, query(RR(rt), l, r) );    return ret;}int main(){    int n, m, i, a, b, val;    while(scanf("%d%d",&n,&m)!=EOF)     {        for(i=1; i<=n; ++i) scanf("%d",&num[i]);        build(1,1,n);        char op[10];        while(m--)        {            scanf("%s",op);            if(op[0]=='Q') {                scanf("%d%d",&a,&b);                printf("%d\n", query(1,a,b));            }            else if(op[0]=='U') {                scanf("%d%d",&a,&val);                update(1,a,val);            }        }    }    return 0;}

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