UVA - 11374 Airport Express （最短路）

题目连接：https://vjudge.net/problem/UVA-11374

思路：最短路+记录路径

#include <bits/stdc++.h>
#define MAXN 100005
#define lson num << 1
#define rson num << 1 | 1
using namespace std;
struct node
{
    int l,r;
    int Max,pos;
}tree[MAXN << 2];
int a[MAXN],d1[MAXN],d2[MAXN];
int cur;
void pushup(int num)
{
    tree[num].Max = max(tree[lson].Max,tree[rson].Max);
    if(tree[lson].Max >= tree[rson].Max) tree[num].pos = tree[lson].pos;
    else tree[num].pos = tree[rson].pos;
}
void build(int num,int l,int r) 
{
    tree[num].l = l;
    tree[num].r = r;
    if(l == r) {
        tree[num].Max = a[l];
        tree[num].pos = l;
        return;
    }
    int mid = (l + r) >> 1;
    build(lson,l,mid);
    build(rson,mid + 1,r);
    pushup(num);
}
void query1(int num,int l,int r,int val)
{
    if(tree[num].l == tree[num].r) {
        if(tree[num].Max > val) cur = min(cur,tree[num].l);
        return;
    }
    int mid = (tree[num].l + tree[num].r) >> 1;
    if(tree[num].l == l && tree[num].r == r) {
        if(tree[lson].Max > val) query1(lson,l,mid,val);
        else if(tree[rson].Max > val) query1(rson,mid + 1,r,val);
        return;
    }
    if(r <= mid) query1(lson,l,r,val);
    else if(l > mid) query1(rson,l,r,val);
    else {
        query1(lson,l,mid,val);
        query1(rson,mid + 1,r,val);
    }
}
void query2(int num,int l,int r)
{
    if(tree[num].l == l && tree[num].r == r) {
        if(tree[num].Max > a[cur]) cur = tree[num].pos;
        return;
    }
    int mid = (tree[num].l + tree[num].r) >> 1;
    if(r <= mid) query2(lson,l,r);
    else if(l > mid) query2(rson,l,r);
    else {
        query2(lson,l,mid);
        query2(rson,mid + 1,r);
    }
}
int main(void)
{
    int T,n,m,Max,pos,val,ans;
    scanf("%d",&T);
    while(T--) {
        memset(d1,0,sizeof(d1));
        memset(d2,0,sizeof(d2));
        scanf("%d %d",&n,&m);
        Max = 0;
        for(int i = 1; i <= n; i++) {
            scanf("%d",&a[i]);
            if(a[i] > Max) {
                d1[i] = d1[i - 1] + 1; 
                Max = a[i];
            }
            else d1[i] = d1[i - 1];
        }
        build(1,1,n);
        d2[n] = 1;
        for(int i = n - 1; i >= 1; i--) {
            cur = n + 1;
            query1(1,i + 1,n,a[i]);
            d2[i] = d2[cur] + 1;
        }
        while(m--) {
            ans = cur = 0;
            scanf("%d %d",&pos,&val);
            if(pos != 1) query2(1,1,pos - 1);
            ans += d1[cur];
            if(val > a[cur]) ans++;
            else val = a[cur];
            cur = n + 1;
            if(pos != n) query1(1,pos + 1,n,val);
            ans += d2[cur];
            printf("%d\n",ans);
        } 
    }
    return 0;
}
/*
1
5 3
1 2 3 4 4
1 5
5 5
2 3
*/