题目大意：
就是给定一堆位置，进行删除还原，最后找到 t 位置上的最大连续位置
1 #include <cstdio> 2 #include <cstring> 3 #include <iostream> 4 5 using namespace std; 6 const int N = 50005; 7 8 struct Node{ 9 int l , r , ml , mr , ma; //ml左最长，mr右最长，ma总最长 10 }tree[N<<2]; 11 12 void build(int o , int l , int r) 13 { 14 tree[o].l = l; 15 tree[o].r = r; 16 tree[o].ml = r - l + 1; 17 tree[o].mr = r - l + 1; 18 tree[o].ma = r - l + 1; 19 int m = (l + r) / 2; 20 if(l == r) return ; 21 build(o<<1 , l , m); 22 build(o<<1|1 , m+1 , r); 23 } 24 25 void push_up(int o) 26 { 27 int ls = o<<1 , rs = o<<1|1; 28 tree[o].ml = tree[ls].ml; 29 tree[o].mr = tree[rs].mr; 30 31 if(tree[ls].ml == (tree[ls].r - tree[ls].l + 1)) 32 tree[o].ml = tree[ls].ml + tree[rs].ml; 33 34 if(tree[rs].mr == (tree[rs].r - tree[rs].l + 1)) 35 tree[o].mr = tree[ls].mr + tree[rs].mr; 36 37 tree[o].ma = max(tree[ls].mr + tree[rs].ml , tree[rs].ma); 38 tree[o].ma = max(tree[ls].ma , tree[o].ma); 39 } 40 41 void update(int o , int t , int v) 42 { 43 if(tree[o].l == tree[o].r){ 44 if(v == 1) tree[o].ma = tree[o].ml = tree[o].mr = 1; 45 else tree[o].ma = tree[o].ml = tree[o].mr = 0; 46 return ; 47 } 48 int ls = o<<1 , rs = o<<1|1; 49 int m = (tree[o].l + tree[o].r) / 2; 50 51 if(t <= m) update(ls , t , v); 52 else update(rs , t , v); 53 //要等下层更新完才能递归回去更新上层 54 push_up(o); 55 } 56 57 int query(int o , int t) 58 { 59 int ls = o<<1 , rs = o<<1|1 , m = (tree[o].l + tree[o].r) / 2; 60 if(tree[o].l == tree[o].r || tree[o].ma == 0 || tree[o].ma == tree[o].r - tree[o].l + 1) 61 return tree[o].ma; 62 63 if(t <= m){ 64 /*此时t属于左子树，那么存在t只属于左子树区间，和属于左右子树合并的区间 65 ，弱属于合并的区间，那么要保证，t到左子树右端点形成的连续的个数要小于 66 左子树最大右端连续和 67 也就是 m - t + 1 <= tree[ls].mr (这里m也等于tree[ls].r) 68 */ 69 if(t >= tree[ls].r - tree[ls].mr + 1) 70 return query(ls , t) + query(rs , m+1); 71 else return query(ls , t); 72 }else{ 73 if(t <= tree[rs].l + tree[rs].ml - 1) 74 return query(ls , m) + query(rs , t); 75 else query(rs , t); 76 } 77 } 78 79 int que[N] , top; 80 81 int main() 82 { 83 // freopen("a.in" , "r" , stdin); 84 int n,m; 85 char str[10]; 86 int x; 87 while(scanf("%d%d",&n,&m)!=EOF){ 88 build(1,1,n); 89 top=0; 90 while(m--) 91 { 92 scanf("%s",str); 93 if(str[0]=='D'){ 94 scanf("%d",&x); 95 que[top++]=x; 96 update(1,x,0); 97 } 98 else if(str[0]=='Q'){ 99 scanf("%d",&x); 100 printf("%d ",query(1,x)); 101 } 102 else{ 103 if(x>0){ 104 x=que[--top]; 105 update(1,x,1); 106 } 107 } 108 } 109 } 110 return 0; 111 }