题目链接：
hdu:http://acm.hdu.edu.cn/showproblem.php?pid=5200
bc(中文):http://bestcoder.hdu.edu.cn/contests/contest_chineseproblem.php?cid=574&pid=1003
题解：
把输入按照高度排序，离线处理出所有高度的答案，每次查询的时候二分查找（upper_bound)。
1 #include<iostream> 2 #include<cstring> 3 #include<cstdio> 4 #include<algorithm> 5 using namespace std; 6 7 const int maxn = 50101; 8 const int mod = 1e9 + 7; 9 typedef long long LL; 10 11 struct Node { 12 int id, h; 13 bool operator < (const Node& rhm) const { 14 return h<rhm.h; 15 } 16 }nds[maxn]; 17 18 int n, q; 19 int ans[maxn]; 20 bool cuted[maxn]; 21 // int fa[maxn]; 22 23 void init() { 24 // for(int i=0;i<maxn;i++) fa[i]=i; 25 memset(cuted, 0, sizeof(cuted)); 26 cuted[0] = cuted[n + 1] = 1; 27 } 28 29 int solve(int x) { 30 //超出去的部分要先处理掉 31 if (x<nds[0].h) return 1; 32 if (x >= nds[n - 1].h) return 0; 33 int low = 0, hig = n; 34 while (low + 1<hig) { 35 int mid = low + (hig - low) / 2; 36 if (nds[mid].h <= x) low = mid; 37 else hig = mid; 38 } 39 return ans[low]; 40 } 41 42 int main() { 43 while (scanf("%d%d", &n, &q) == 2 && n) { 44 init(); 45 for (int i = 0; i<n; i++) { 46 scanf("%d", &nds[i].h); 47 nds[i].id = i + 1; 48 } 49 sort(nds, nds + n); 50 int num = 1; 51 for (int i = 0; i<n; i++) { 52 int id = nds[i].id; 53 if (!cuted[id - 1] && !cuted[id + 1]) { 54 num++; 55 } 56 else if (cuted[id - 1] && cuted[id + 1]) { 57 num--; 58 } 59 cuted[id] = 1; 60 ans[i] = num; 61 } 62 while (q--) { 63 int x; 64 scanf("%d", &x); 65 printf("%d ", solve(x)); 66 } 67 } 68 return 0; 69 } 70 /* 71 1 100 72 1 73 0 74 2 75 */
直接用upper_bound():
1 #include<iostream> 2 #include<cstring> 3 #include<cstdio> 4 #include<algorithm> 5 using namespace std; 6 7 const int maxn = 50101; 8 const int mod = 1e9 + 7; 9 typedef long long LL; 10 11 struct Node { 12 int id, h; 13 Node(int id, int h) :id(id), h(h) {} 14 Node() {} 15 bool operator < (const Node& rhm) const { 16 return h<rhm.h; 17 } 18 }nds[maxn]; 19 20 int n, q; 21 int ans[maxn]; 22 bool cuted[maxn]; 23 // int fa[maxn]; 24 25 void init() { 26 // for(int i=0;i<maxn;i++) fa[i]=i; 27 memset(cuted, 0, sizeof(cuted)); 28 cuted[0] = cuted[n + 1] = 1; 29 } 30 31 int solve(int x) { 32 //超出去的部分要先处理掉 33 if (x<nds[0].h) return 1; 34 if (x >= nds[n - 1].h) return 0; 35 //upper_bound找到的是x后面的一个数，所以要减一 36 return ans[upper_bound(nds, nds + n, Node(0,x))-nds-1]; 37 } 38 39 int main() { 40 while (scanf("%d%d", &n, &q) == 2 && n) { 41 init(); 42 for (int i = 0; i<n; i++) { 43 scanf("%d", &nds[i].h); 44 nds[i].id = i + 1; 45 } 46 sort(nds, nds + n); 47 int num = 1; 48 for (int i = 0; i<n; i++) { 49 int id = nds[i].id; 50 if (!cuted[id - 1] && !cuted[id + 1]) { 51 num++; 52 } 53 else if (cuted[id - 1] && cuted[id + 1]) { 54 num--; 55 } 56 cuted[id] = 1; 57 ans[i] = num; 58 } 59 while (q--) { 60 int x; 61 scanf("%d", &x); 62 printf("%d ", solve(x)); 63 } 64 } 65 return 0; 66 } 67 /* 68 1 100 69 1 70 0 71 2 72 */