題目鏈接：http://acm.hdu.edu.cn/showproblem.php?pid=1540

解題思路：線段樹節點增加一個ld----區間左端點起始的最大長度，rd----區間右端點起始的最大長度，md----覆蓋區間中點的最大長度，那么對于每次更新，更新到點然后更新父節點值；對于每次查詢，若為中點，則返回md，否則從左右孩子中選擇。需要注意的是ld，rd與md可能會有重疊部分，因此更新與查詢的時候需要判斷一下。

代碼：

1 const int maxn = 5e4 + 5; 2 3 int ld[maxn * 4], rd[maxn * 4], md[maxn * 4]; 4 int ok[maxn]; 5 int n, m; 6 stack<int> s; 7 8 void build(int l, int r, int k){ 9 ld[k] = rd[k] = md[k] = (r - l + 1); 10 if(l == r) return; 11 int mid = (l + r) >> 1, lc = k << 1, rc = k << 1 | 1; 12 build(l, mid, lc); 13 build(mid + 1, r, rc); 14 } 15 void update(int u, int x, int l, int r, int k){ 16 if(u == l && l == r){ 17 if(x == 0) 18 ld[k] = rd[k] = md[k] = 0; 19 else 20 ld[k] = rd[k] = md[k] = 1; 21 return; 22 } 23 int mid = (l + r) >> 1, lc = k << 1, rc = k << 1 | 1; 24 if(u <= mid) update(u, x, l, mid, lc); 25 else update(u, x, mid + 1, r, rc); 26 ld[k] = (ld[lc] >= mid - l + 1)? ld[lc] + ld[rc]: ld[lc]; 27 rd[k] = (rd[rc] >= r - mid)? rd[rc] + rd[lc]: rd[rc]; 28 md[k] = rd[lc] == 0? 0: ld[rc] + rd[lc]; 29 } 30 int query(int u, int l, int r, int k){ 31 int mid = (l + r) >> 1, lc = k << 1, rc = k << 1 | 1; 32 if(u == mid) return md[k]; 33 if(u <= mid) { 34 int q1 = query(u, l, mid, lc); 35 if(rd[lc] >= mid - u + 1) q1 += ld[rc]; 36 return q1; 37 } 38 else{ 39 int q2 = query(u, mid + 1, r, rc); 40 if(ld[rc] >= u - mid) q2 += rd[lc]; 41 return q2; 42 } 43 } 44 int main(){ 45 while(scanf("%d %d", &n, &m) != EOF){ 46 while(!s.empty()) s.pop(); 47 build(1, n, 1); 48 for(int i = 1; i <= n; i++) ok[i] = 1; 49 while(m--){ 50 char ch; 51 scanf(" %c", &ch); 52 if(ch == 'D'){ 53 int u; 54 scanf("%d", &u); 55 if(ok[u]) update(u, 0, 1, n, 1); 56 ok[u] = 0; 57 s.push(u); 58 } 59 else if(ch == 'Q'){ 60 int u; 61 scanf("%d", &u); 62 int tmans = query(u, 1, n, 1); 63 printf("%d\n", tmans); 64 } 65 else{ 66 if(!s.empty()){ 67 int u = s.top(); 68 s.pop(); 69 if(!ok[u]) update(u, 1, 1, n, 1); 70 ok[u] = 1; 71 } 72 } 73 } 74 } 75 }

題目：

Tunnel Warfare

Time Limit: 4000/2000 MS (Java/Others)????Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 9320????Accepted Submission(s): 3633

Problem Description During the War of Resistance Against Japan, tunnel warfare was carried out extensively in the vast areas of north China Plain. Generally speaking, villages connected by tunnels lay in a line. Except the two at the ends, every village was directly connected with two neighboring ones.

Frequently the invaders launched attack on some of the villages and destroyed the parts of tunnels in them. The Eighth Route Army commanders requested the latest connection state of the tunnels and villages. If some villages are severely isolated, restoration of connection must be done immediately! ?

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Input The first line of the input contains two positive integers n and m (n, m ≤ 50,000) indicating the number of villages and events. Each of the next m lines describes an event.

There are three different events described in different format shown below:

D x: The x-th village was destroyed.

Q x: The Army commands requested the number of villages that x-th village was directly or indirectly connected with including itself.

R: The village destroyed last was rebuilt. ?

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Output Output the answer to each of the Army commanders’ request in order on a separate line. ?

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Sample Input 7 9 D 3 D 6 D 5 Q 4 Q 5 R Q 4 R Q 4 ?

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Sample Output 1 0 2 4 ?

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Source POJ Monthly

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轉載于:https://www.cnblogs.com/bolderic/p/7302645.html

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