310075: CF1779C. Least Prefix Sum
Memory Limit:256 MB
Time Limit:2 S
Judge Style:Text Compare
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Description
Least Prefix Sum
题意翻译
定义长度为 $n$ 的数组 $arr$ 的前缀和数组为 $s$,对于一次操作,你可以选择一个数,变为这个数的相反数,给定一个数 $m$,请你求出最小的操作次数使序列满足:$\forall i\in[1,n], s_i\geq s_m$。题目描述
Baltic, a famous chess player who is also a mathematician, has an array $ a_1,a_2, \ldots, a_n $ , and he can perform the following operation several (possibly $ 0 $ ) times: - Choose some index $ i $ ( $ 1 \leq i \leq n $ ); - multiply $ a_i $ with $ -1 $ , that is, set $ a_i := -a_i $ . Baltic's favorite number is $ m $ , and he wants $ a_1 + a_2 + \cdots + a_m $ to be the smallest of all non-empty prefix sums. More formally, for each $ k = 1,2,\ldots, n $ it should hold that $ $a_1 + a_2 + \cdots + a_k \geq a_1 + a_2 + \cdots + a_m. $ $ </p><p>Please note that multiple smallest prefix sums may exist and that it is only required that $ a\_1 + a\_2 + \\cdots + a\_m $ is one of them.</p><p>Help Baltic find the minimum number of operations required to make $ a\_1 + a\_2 + \\cdots + a\_m$ the least of all prefix sums. It can be shown that a valid sequence of operations always exists.输入输出格式
输入格式
Each test contains multiple test cases. The first line contains the number of test cases $ t $ ( $ 1 \leq t \leq 10\,000 $ ). The description of the test cases follows. The first line of each test case contains two integers $ n $ and $ m $ ( $ 1 \leq m \leq n \leq 2\cdot 10^5 $ ) — the size of Baltic's array and his favorite number. The second line contains $ n $ integers $ a_1,a_2, \ldots, a_n $ ( $ -10^9 \leq a_i \leq 10^9 $ ) — the array. It is guaranteed that the sum of $ n $ over all test cases does not exceed $ 2\cdot 10^5 $ .
输出格式
For each test case, print a single integer — the minimum number of required operations.
输入输出样例
输入样例 #1
6
4 3
-1 -2 -3 -4
4 3
1 2 3 4
1 1
1
5 5
-2 3 -5 1 -20
5 2
-2 3 -5 -5 -20
10 4
345875723 -48 384678321 -375635768 -35867853 -35863586 -358683842 -81725678 38576 -357865873
输出样例 #1
1
1
0
0
3
4