直接搞吧，就是用栈存复原点时要判下栈顶指针是否空。不然会wa在Hdu上。ps：打日本鬼子的题，必须ac啊
#include <cstdio> #include <cstring> #include <algorithm> #include <climits> #include <string> #include <iostream> #include <map> #include <cstdlib> #include <list> #include <set> #include <queue> #include <stack> #include<math.h> using namespace std; #define lson l,mid,rt<<1 #define rson mid+1,r,rt<<1|1 const int maxn = 55555; int sum[maxn << 2]; int lsum[maxn << 2]; int rsum[maxn << 2]; void up(int rt, int m) { lsum[rt] = lsum[rt << 1]; rsum[rt] = rsum[rt << 1 | 1]; if (lsum[rt] == (m - (m >> 1))) lsum[rt] += lsum[rt << 1 | 1]; if (rsum[rt] == (m >> 1)) rsum[rt] += rsum[rt << 1]; sum[rt] = max(max(sum[rt << 1], sum[rt << 1 | 1]), rsum[rt << 1] + lsum[rt << 1 | 1]); } void build(int l, int r, int rt) { if (l == r){ sum[rt] = lsum[rt] = rsum[rt] = 1; return; } int mid = (l + r) >> 1; build(lson); build(rson); up(rt, r - l + 1); } void update(int key, int add, int l, int r, int rt) { if (l == r){ if (add) sum[rt] = lsum[rt] = rsum[rt] = 0; if (!add) sum[rt] = lsum[rt] = rsum[rt] = 1; return; } int mid = (l + r) >> 1; if (key <= mid) update(key, add, lson); else update(key, add, rson); up(rt, r - l + 1); } int ask(int key, int l, int r, int rt) { if (l == r){ if (sum[rt] == 1) return 1; return 0; } int mid = (l + r) >> 1; int a = l + lsum[rt] - 1; int b = r - rsum[rt] + 1; int ans = 0; if (key >= l&&key <= a) ans = lsum[rt]; if (key >= b&&key <= r) ans = max(ans, rsum[rt]); int c = mid - rsum[rt << 1] + 1; int d = lsum[rt << 1 | 1] + mid; if (key >= c&&key <= d) ans = max(ans, rsum[rt << 1] + lsum[rt << 1 | 1]); if (ans) return ans; if (key <= mid) return ask(key, lson); else return ask(key, rson); } int q[maxn<<1]; int main() { int n, m; int a; char str[100]; while (scanf("%d%d",&n,&m)!=EOF){ build(1, n, 1); int ans = 0; for (int i = 0; i < m; i++){ scanf("%s%d", str, &a); if (str[0] == 'D'){ update(a, 1, 1, n, 1); q[ans++] = a; } if (str[0] == 'Q'){ printf("%d ", ask(a, 1, n, 1)); } if (str[0] == 'R'){ if(ans<=0) continue; int t = q[--ans]; update(t, 0, 1, n, 1); } } } return 0; }