区间合并 POJ3667+HDU4553

两道题都是线段树的区间合并

lsum, rsum分别表示左/右端点 开始向右/左 符合条件的元素的最长连续长度

sum表示这个区间的符合条件的元素的最长连续长度

所以pushUp可写：

 void pushUp(int root, int l, int r)
 {
     int len = r - l + ;
     int lenr = len >> , lenl = len - lenr;
     lsum[root] = lsum[lson];
     rsum[root] = rsum[rson];
     if (lsum[root] == lenl) lsum[root] += lsum[rson];
     if (rsum[root] == lenr) rsum[root] += rsum[lson];
     sum[root] = max(rsum[lson]+lsum[rson], max(sum[lson], sum[rson]));
 }

更新时 根据更新的元素的值 可以确定 这个区间的sum lsum 和 rsum 是len 还是 0

所以pushDown 和 update可以写了

这里放pushDown

 void pushDown(int root, int l, int r)
 {
     int len = r - l + ;
     int lenr = len >> , lenl = len - lenr;
     if (setmark[root] != -)
     {
         int v = setmark[root];
         setmark[lson] = setmark[rson] = v;
         setmark[root] = -;
         lsum[lson] = rsum[lson] = sum[lson] = v ?  : lenl;//被占用是1 不被占用是0
         lsum[rson] = rsum[rson] = sum[rson] = v ?  : lenr;
     }
 }

另外注意的是query的方式

 int query(int root, int l, int r, int qlen)
 {
     if (l == r) return l;
     pushDown(root, l, r);
     int mid = (l+r) >> ;
     if (sum[lson] >= qlen) return query(lson, l, mid, qlen);
     else if (rsum[lson]+lsum[rson] >= qlen) return mid-rsum[lson]+;//左区间的右半部份 和右区间的左半部份
     else if return query(rson, mid+, r, qlen);
 }

如果不存在直接求sum[1]是否>=qlen

POJ3667

元素只有1 和 0两种情况 用一个维护一个区间最长连续和即可

代码君：

 #include <string.h>
 #include <stdio.h>
 #include <algorithm>
 #include <iostream>
 #define lson root<<1
 #define rson root<<1|1
 #define fi first
 #define se second
 #define pb push_back
 #define po pop_back

 typedef long long ll;

 const int MAXN = ;
 const int MAXM = ;
 const int INF = 0x3f3f3f3f;

 using namespace std;

 int n, m;
 int sum[MAXN << ];
 int setmark[MAXN << ];
 int lsum[MAXN << ];
 int rsum[MAXN << ];

 void pushUp(int root, int l, int r)
 {
     int len = r - l + ;
     int lenr = len >> , lenl = len - lenr;
     lsum[root] = lsum[lson];
     rsum[root] = rsum[rson];
     if (lsum[root] == lenl) lsum[root] += lsum[rson];
     if (rsum[root] == lenr) rsum[root] += rsum[lson];
     sum[root] = max(rsum[lson]+lsum[rson], max(sum[lson], sum[rson])); //这个地方 理解！
 }
 void build(int root, int l, int r)
 {
     int len = r-l+;
     setmark[root] = -;
     lsum[root] = rsum[root] = sum[root] = len;
     if (l == r) return ;
     int mid = (l+r) >> ;
     build(lson, l, mid);
     build(rson, mid+, r);
     pushUp(root, l, r);
 }
 void pushDown(int root, int l, int r)
 {
     int len = r - l + ;
     int lenr = len >> , lenl = len - lenr;
     if (setmark[root] != -)
     {
         int v = setmark[root];
         setmark[lson] = setmark[rson] = v;
         setmark[root] = -;
         lsum[lson] = rsum[lson] = sum[lson] = v ?  : lenl;//被占用是1 不被占用是0
         lsum[rson] = rsum[rson] = sum[rson] = v ?  : lenr;
     }
 }
 void update(int root, int l, int r, int ul, int ur, int val)
 {
     int len = r - l + ;
     int lenr = len >> , lenl = len - lenr;
     if (l > ur || r < ul) return ;
     if (l >= ul && r <= ur)
     {
         setmark[root] = val;
         lsum[root] = rsum[root] = sum[root] = val ?  : len;
         return ;
     }
     pushDown(root, l, r);
     int mid = (l+r) >> ;
     update(lson, l, mid, ul, ur, val);
     update(rson, mid+, r, ul, ur, val);
     pushUp(root, l, r);
 }
 int query(int root, int l, int r, int qlen)
 {
     if (l == r) return l;
     pushDown(root, l, r);
     int mid = (l+r) >> ;
     if (sum[lson] >= qlen) return query(lson, l, mid, qlen);
     if (rsum[lson]+lsum[rson] >= qlen) return mid-rsum[lson]+;//左区间的右半部份 和右区间的左半部份
     if (sum[rson] >= qlen) return query(rson, mid+, r, qlen);
     return -;
 }
 int main()
 {
     //freopen("in.txt", "r", stdin);
     while (cin >> n >> m)
     {
         build(, , n);
         for(int i = ; i < m; i++)
         {
             int op, p, l;
             scanf("%d", &op);
             if (op == )
             {
                 scanf("%d", &l);
                 if (sum[] < l)
                 {
                     puts("");
                     continue;
                 }
                 int pos = query(, , n, l);
                 cout << pos << endl;
                 update(, , n, pos, pos+l-, );
             }
             else
             {
                 scanf("%d%d", &p, &l);
                 //cout << p << " " << p+l-1 << endl;
                 update(, , n, p, p+l-, );
             }
         }
     }
     return ;
 }

HDU4553

元素有0 1 2三种情况 需要维护两个区间最长连续和

代码君：

 #include <bits/stdc++.h>
 #define lson root<<1
 #define rson root<<1|1
 #define fi first
 #define se second
 #define pb push_back
 #define po pop_back

 using namespace std;

 typedef long long ll;
 typedef pair<int, int> P;

 const int MAXN = 1e5+;
 const int MAXM = 1e5+;
 const int INF = 0x3f3f3f3f;

 //0 for diaosi  1 for nvshen
 int sum[][MAXN << ];
 int lsum[][MAXN << ];
 int rsum[][MAXN << ];
 int setmark[MAXN << ];
 int pos = -;
 int qlen = -;
 int n, m;
 void pushUp(int root, int l, int r, int nu)
 {
     int len = r-l+;
     int lenr = len >> , lenl = len - lenr;
     lsum[nu][root] = lsum[nu][lson];
     if (lsum[nu][root] == lenl) lsum[nu][root] += lsum[nu][rson];
     rsum[nu][root] = rsum[nu][rson];
     if (rsum[nu][root] == lenr) rsum[nu][root] += rsum[nu][lson];
     sum[nu][root] = max(rsum[nu][lson]+lsum[nu][rson], max(sum[nu][lson], sum[nu][rson]));
 }
 void build(int root, int l, int r)
 {
     int len = r - l + ;
     setmark[root] = -;
     for (int i = ; i < ; i++)
     {
         sum[i][root] = lsum[i][root] = rsum[i][root] = len;
     }
     if (l == r) return ;
     int mid = (l+r) >> ;
     build(lson, l, mid);
     build(rson, mid+, r);
     for (int i = ; i < ; i++)
     pushUp(root, l, r, i);
 }
 void pushDown(int root, int l, int r)
 {
     int len = r - l + ;
     int lenr = len >> , lenl = len - lenr;
     if (setmark[root] != -)
     {
         int val = setmark[root];
         setmark[lson] = setmark[rson] = val;
         setmark[root] = -;
         lsum[][lson] = rsum[][lson] = sum[][lson] = (val ==  ? lenl : );
         lsum[][rson] = rsum[][rson] = sum[][rson] = (val ==  ? lenr : );
         lsum[][lson] = rsum[][lson] = sum[][lson] = ( (val ==  || val == ) ? lenl : );
         lsum[][rson] = rsum[][rson] = sum[][rson] = ( (val ==  || val == ) ? lenr : );
     }
 }
 void update(int root, int l, int r, int ul, int ur, int val)
 {
     int len = r - l + ;
     if (l > ur || r < ul) return;
     if (l >= ul && r <= ur)
     {
         setmark[root] = val;
         lsum[][root] = rsum[][root] = sum[][root] = (val ==  ? len : );
         lsum[][root] = rsum[][root] = sum[][root] = ((val ==  || val == ) ? len : );
         return ;
     }
     pushDown(root, l, r);
     int mid = (l+r) >> ;
     update(lson, l, mid, ul, ur, val);
     update(rson, mid+, r, ul, ur, val);
     for (int i = ; i < ; i++)
     pushUp(root, l, r, i);
 }

 int query(int root, int l, int r, int qlen, int nu)
 {
     if (l == r)    return l;
     pushDown(root, l, r);
     int mid = (l+r) >> ;
     if (sum[nu][lson] >= qlen) return query(lson, l, mid, qlen, nu);
     else if (rsum[nu][lson] + lsum[nu][rson] >= qlen) return mid - rsum[nu][lson] + ;
     else return query(rson, mid+, r, qlen, nu);
 }
 int main()
 {
     //注意都是英文符号
     //freopen("in.txt", "r", stdin);
     int T;
     scanf("%d", &T);
     for (int cas = ; cas <= T; cas++)
     {
         printf("Case %d:\n", cas);
         scanf("%d%d", &n, &m);
         build(, , n);
         for (int i = ; i < m; i++)
         {
             char buf[];
             int qlen;
             scanf("%s", buf);
             if (buf[] == 'D')
             {
                 scanf("%d", &qlen);
                 int pos = -;
                 if (qlen > n || sum[][] < qlen)
                 {
                     puts("fly with yourself");
                     continue;
                 }
                 pos = query(, , n, qlen, );
                 printf("%d,let's fly\n", pos);
                 update(, , n, pos, pos+qlen-, );
             }
             else if (buf[] == 'N')
             {
                 scanf("%d", &qlen);
                 int pos = -;
                 if (qlen > n || sum[][] < qlen)
                 {
                     puts("wait for me");
                     continue;
                 }
                 if (sum[][] >= qlen) pos = query(, , n, qlen, );
                 else pos = query(, , n, qlen, );
                 printf("%d,don't put my gezi\n", pos);
                 update(, , n, pos, pos+qlen-, );
             }
             else
             {
                 int l, r;
                 scanf("%d%d", &l, &r);
                 update(, , n, l, r, );
                 puts("I am the hope of chinese chengxuyuan!!");
             }
         }
     }
     return ;
 }