Tunnel Warfare 线段树 区间合并|最大最小值

时间:2021-02-14 21:58:52

B - Tunnel WarfareHDU - 1540

这个有两种方法,一个是区间和并,这个我个人感觉异常恶心

第二种方法就是找最大最小值 kuangbin——线段树专题 H - Tunnel Warfare <-- 这个博客讲的很清楚

#include <cstdio>//法一:最大值最小值法,这个就是每一个点,如果这个点没有被摧毁,那就找到这个点最左边的和最右边的
#include <cstdlib>//最大-最小+1.这个就是这个最大连续长度。
#include <queue>//建树,很简单,主要就是query和update。
#include <algorithm>//这个地方的怎么去找一个包含一个数的一个区间的最大最小值呢?
#include <vector>//这个就是从上面往下面查询的过程中,就去找,如果是找最大值就去max,最小值就取min
#include <cstring>//这个要注意建树,这个区间的最大值的意思是,小于等于这个数的最大的被炸了的村庄,这个就说明,开始最大值为0,因为没有任何一个村庄被炸
#include <string>//区间的最小值,意思是大于等于这个数,被炸了的村庄的最小值,开始为n+1.因为没有村庄被炸。
#include <iostream>
#include <stack>
#define inf 0x3f3f3f3f
using namespace std;
const int maxn = 1e5 + ;
struct node
{
int l, r;
int mx, mn;
}tree[maxn*];
int n;
void build(int id,int l,int r)
{
tree[id].l = l;
tree[id].r = r;
if(l==r)
{
tree[id].mn = n+;
tree[id].mx = ;
return;
}
int mid = (l + r) >> ;
build(id << , l, mid);
build(id << | , mid + , r);
tree[id].mx = max(tree[id << ].mx, tree[id << | ].mx);
tree[id].mn = min(tree[id << ].mn, tree[id << | ].mn);
} void update_max(int id,int x,int z)
{
if(tree[id].l==tree[id].r)
{
tree[id].mx = z;
return;
}
int mid = (tree[id].l + tree[id].r) >> ;
if(x<=mid) update_max(id << , x, z);
if (x > mid) update_max(id << | , x, z);
tree[id].mx = max(tree[id << ].mx, tree[id << | ].mx);
} void update_min(int id,int x,int z)
{
if(tree[id].l==tree[id].r)
{
tree[id].mn = z;
return;
}
int mid = (tree[id].l + tree[id].r) >> ;
if (x <= mid) update_min(id << , x, z);
if (x > mid) update_min(id << | , x, z);
tree[id].mn = min(tree[id << ].mn, tree[id << | ].mn);
} int query_max(int id,int x,int y)
{
int ans = ;
if(x<=tree[id].l&&y>=tree[id].r)
{
return tree[id].mx;
}
int mid = (tree[id].l + tree[id].r) >> ;
if (x <= mid) ans = max(ans, query_max(id << , x, y));
if (y > mid) ans = max(ans, query_max(id << | , x, y));
return ans;
} int query_min(int id,int x,int y)
{
int ans = inf;
if(x<=tree[id].l&&y>=tree[id].r)
{
return tree[id].mn;
}
int mid = (tree[id].l + tree[id].r) >> ;
if (x <= mid) ans = min(ans, query_min(id << , x, y));
if (y > mid) ans = min(ans, query_min(id << | , x, y));
return ans;
} int main()
{ int m, x;
while(cin >> n >> m)
{
stack<int>sta;
build(, , n);
while(m--)
{
char s[];
scanf("%s", s);
if(s[]=='D')
{
cin >> x;
update_max(, x, x);
update_min(, x, x);
sta.push(x);
}
if(s[]=='R')
{
int y = sta.top(); sta.pop();
update_max(, y, );
update_min(, y, n + );
}
if(s[]=='Q')
{
cin >> x;
int L = query_min(, x, n + );
int R = query_max(, , x);
//printf("%d %d\n", L, R);
if (L == R) printf("0\n");
else printf("%d\n", L - R - );
}
}
} return ;
}

方法一

//法二:区间合并,这个应该更好懂一点,就是维护一下一个区间的前缀后缀长度
//这个更新应该比较简单,
#include <cstdio>
#include <cstdlib>
#include <queue>
#include <algorithm>
#include <vector>
#include <cstring>
#include <string>
#include <iostream>
#include <stack>
#define inf 0x3f3f3f3f
using namespace std;
const int maxn = 1e5 + ;
struct node
{
int l, r, len;
int max_pre, max_last;
}tree[maxn*]; void push_up(int id)
{
tree[id].max_pre = tree[id << ].max_pre;
tree[id].max_last = tree[id << | ].max_last;
if (tree[id << ].max_pre == tree[id << ].len)
{
tree[id].max_pre += tree[id << | ].max_pre;
}
if(tree[id<<|].max_last==tree[id<<|].len)
{
tree[id].max_last += tree[id << ].max_last;
}
} void build(int id,int l,int r)
{
tree[id].l = l;
tree[id].r = r;
tree[id].len = r - l + ;
if(l==r)
{
tree[id].max_pre = tree[id].max_last = ;
return;
}
int mid = (l + r) >> ;
build(id << , l, mid);
build(id << | , mid + , r);
push_up(id);
} void update(int id,int x,int z)
{
if(tree[id].l==tree[id].r)
{
tree[id].max_pre = z;
tree[id].max_last = z;
return;
}
int mid = (tree[id].l + tree[id].r) >> ;
if (x <= mid) update(id << , x, z);
else update(id << | , x, z);
push_up(id);
} int query_pre(int id,int x,int y)
{
int ans = , res = ;
if(x<=tree[id].l&&y>=tree[id].r)
{
//printf("tree[%d].max_pre=%d\n", id, tree[id].max_pre);
return tree[id].max_pre;
}
//printf("id=%d x=%d y=%d\n", id, x, y);
int mid = (tree[id].l + tree[id].r) >> ;
if (x <= mid) ans=query_pre(id << , x, y);
if (y > mid) res=query_pre(id << | , x, y);
//printf("id=%d ans=%d res=%d mid=%d\n",id, ans, res,mid);
if (ans >= mid - x + )
{
//printf("tree[%d].max_pre=%d mid=%d x=%d\n",id, tree[id].max_pre, mid, x);
ans += res;
}
return ans;
} int query_last(int id,int x,int y)
{
int ans = , res = ;
if (x <= tree[id].l&&y >= tree[id].r)
{
//printf("tree[%d].last=%d\n", id, tree[id].max_last);
return tree[id].max_last;
}
//printf("id=%d x=%d y=%d\n", id, x, y);
int mid = (tree[id].l + tree[id].r) >> ;
if (x <= mid) ans = query_last(id << , x, y);
if (y > mid) res = query_last(id << | , x, y);
//printf("id=%d mid=%d ans=%d res=%d\n", id, mid,ans, res);
if (res >= y-mid)
{
//printf("tree[%d].max_last=%d mid=%d x=%d\n",id,tree[id].max_last, mid, x);
res += ans;
}
return res;
} int main()
{
int n, m;
while(scanf("%d %d",&n,&m)!=EOF)
{
stack<int>sta;
build(, , n);
while(m--)
{
char s[];
scanf("%s", s);
if(s[]=='D')
{
int x;
cin >> x;
update(, x, );
sta.push(x);
}
if(s[]=='R')
{
int y = sta.top(); sta.pop();
update(, y, );
}
if(s[]=='Q')
{
int x;
cin >> x;
int ans = query_pre(, x, n);
ans += query_last(, , x);
if(ans) printf("%d\n", ans-);
else printf("0\n");
}
}
}
return ;
}
/*
7 10
D 3
D 6
D 5
Q 4
Q 5
R
Q 4
R
Q 4
Q 3
*/

方法二