sicily 1137 河床 (二分分治)

 1 //1137.河床
 2 #include <iostream>
 3 using namespace std;
 4 
 5 int max_length(int d[], int l, int r, int m) {
 6     //计算最大长度并返回
 7     //d为保存高度的数组
 8     //l为下标左界
 9     //r为下标右界
10     //m为最大高度差
11     if (l==r) return 1;
12     if (l==r-1) {
13         if ((d[l]-d[r]<=m)&&(d[l]-d[r]>=-m)) return 2;
14         else return 1;
15     }
16     //二分
17     int mid = (l+r)/2;
18     int lm = max_length(d,l,mid,m);
19     int rm = max_length(d,mid+1,r,m);
20     int mm = 1;
21     int min , max;
22     min = max = d[mid];
23     for (int i = mid-1; i >= l; i--) {
24         if ((d[i]>=max-m)&&(d[i]<=min+m)) {
25             ++mm;
26             if (d[i]<min) min = d[i];
27             else if (d[i]>max) max = d[i];
28         }
29         else break;
30     }
31     for (int i = mid+1; i <= r; i++) {
32         if ((d[i]>=max-m)&&(d[i]<=min+m)) {
33             ++mm;
34             if (d[i]<min) min = d[i];
35             else if (d[i]>max) max = d[i];
36         }
37         else break;
38     }
39     //返回最大值
40     return (lm>rm?lm:rm)>mm?(lm>rm?lm:rm):mm;
41 }
42 
43 int main() {
44     int n, m;
45     cin>>n>>m;
46     int d[n];
47     for (int i = 0; i < n; i++) cin>>d[i];
48     cout<<max_length(d,0,n-1,m)<<endl;
49     return 0;
50 }