B. Code For 1 分治
Jon fought bravely to rescue the wildlings who were attacked by the white-walkers at Hardhome. On his arrival, Sam tells him that he wants to go to Oldtown to train at the Citadel to become a maester, so he can return and take the deceased Aemon's place as maester of Castle Black. Jon agrees to Sam's proposal and Sam sets off his journey to the Citadel. However becoming a trainee at the Citadel is not a cakewalk and hence the maesters at the Citadel gave Sam a problem to test his eligibility.
Initially Sam has a list with a single element n. Then he has to perform certain operations on this list. In each operation Sam must remove any element x, such that x > 1, from the list and insert at the same position , , sequentially. He must continue with these operations until all the elements in the list are either 0 or 1.
Now the masters want the total number of 1s in the range l to r (1-indexed). Sam wants to become a maester but unfortunately he cannot solve this problem. Can you help Sam to pass the eligibility test?
The first line contains three integers n, l, r (0 ≤ n < 250, 0 ≤ r - l ≤ 105, r ≥ 1, l ≥ 1) – initial element and the range l to r.
It is guaranteed that r is not greater than the length of the final list.
Output the total number of 1s in the range l to r in the final sequence.
7 2 5
4
10 3 10
5
Consider first example:
这个题目做的挺漂亮嘛!哈哈!
#include<cstdio> #include<algorithm> #include<cmath> #include<vector> #include<iostream> #define MAXN 200009 #define eps 1e-11 + 1e-12/2 typedef long long LL; using namespace std; /* 显然!分治! */ LL n, l ,r; LL solve(LL x, LL beg,LL end) { LL mid = (beg + end) / 2; if (beg == mid) return 1; if (r < mid) return solve(x / 2, beg, mid - 1); else if (l > mid) return solve(x / 2, mid + 1, end); else { LL ret = x % 2; if (l < mid) ret += solve(x / 2, beg, mid - 1); if (r > mid) ret += solve(x / 2, mid + 1, end); return ret; } return 0; } int main() { cin >> n >> l >> r; if (n == 0) { cout << 0 << endl; return 0; } LL len = pow(2, floor(log2(n)) + 1) - 1; cout << solve(n, 1, len) << endl; }