Here is the mashup link (the problems are from Codeforces' problem set).

#### A. Save Water

**Solution**

Let's sort the array in nonincreasing order. Now the answer is some of the first containers. Let's iterate over array from left to right until the moment when we will have the sum at least m. The number of elements we took is the answer to the problem.

Complexity: $$$\mathcal{O}(nlogn)$$$.

**Code**

```
n = int(input())
m = int(input())
flash = []
for _ in range(n):
val = int(input())
flash.append(val)
flash.sort(reverse=True)
cur = 0
for i in range(n):
cur += flash[i]
if cur >= m:
print(i + 1)
break
```

#### B. Odd-maker

**Solution**

Note that for each question, the resulting array is

So, the sum of the elements of the new array after each question is

We can compute $$$a_1+⋯+a_{l−1}$$$ and $$$a_{r+1}+⋯+a_n$$$ in $$$\mathcal{O}(1)$$$ time by precomputing the sum of all prefixes and suffixes, or alternatively by using the prefix sums technique. So we can find the sum each time in $$$\mathcal{O}(1)$$$ per question, and just check if it's odd or not. The time complexity is $$$\mathcal{O}(n+q)$$$.

**Code**

```
from itertools import accumulate
from sys import stdin
# Fast input for python. Note that it gives you the input with the newline character, '\n'
# This may cause a problem on string problems. In that case, use stdin.readline()[:-1] to strip the last character('\n')
def input(): return stdin.readline()
T = int(input())
for _ in range(T):
N, Q = map(int, input().split())
a = list(map(int, input().split()))
pref_sum = list(accumulate(a, initial=0))
for __ in range(Q):
l, r, k = map(int, input().split())
left_sum = pref_sum[l - 1]
right_sum = pref_sum[-1] - pref_sum[r]
middle_sum = k*(r - l + 1)
total_sum = left_sum + middle_sum + right_sum
if total_sum%2 == 1:
print("YES")
else:
print("NO")
```

#### C. Yet Another Painting

**Solution**

Note that for each question, the resulting array is

So, the sum of the elements of the new array after each question is

We can compute $$$a_1+⋯+a_{l−1}$$$ and $$$a_{r+1}+⋯+a_n$$$ in $$$\mathcal{O}(1)$$$ time by precomputing the sum of all prefixes and suffixes, or alternatively by using the prefix sums technique. So we can find the sum each time in $$$\mathcal{O}(1)$$$ per question, and just check if it's odd or not. The time complexity is $$$\mathcal{O}(n+q)$$$.

**Code**

```
from itertools import accumulate
from sys import stdin
# Fast input for python. Note that it gives you the input with the newline character, '\n'
# This may cause a problem on string problems. In that case, use stdin.readline()[:-1] to strip the last character('\n')
def input(): return stdin.readline()
T = int(input())
for _ in range(T):
N, Q = map(int, input().split())
a = list(map(int, input().split()))
pref_sum = list(accumulate(a, initial=0))
for __ in range(Q):
l, r, k = map(int, input().split())
left_sum = pref_sum[l - 1]
right_sum = pref_sum[-1] - pref_sum[r]
middle_sum = k*(r - l + 1)
total_sum = left_sum + middle_sum + right_sum
if total_sum%2 == 1:
print("YES")
else:
print("NO")
```

#### D. MaxiSum

**Hint**

There is always one sheep that shouldn't move.

**Solution**

Let's denote by k the number of sheep in the string, and by $$$x_1,x_2,…,x_k$$$ $$$(1≤x_1<x_2<…<x_k≤n)$$$ their positions in the string. Note that in the optimal solution the sheep with the number $$$m=⌈n/2⌉$$$ will not make moves. This can be proved by considering the optimal solution in which the sheep with the number m makes at least one move. if it moves to the right all sheep that are to the left of $$$x_m$$$( $$$x_1,x_2,…,x_{m-1}$$$) will move by one to the right but not all the sheep that are on the left side of $$$x_m$$$( $$$x_{m+1},x{m+2},…,x_k$$$) will decrease their movement by one and same thing if the $$$m-th$$$ sheep move to the left. So we can conclude that this solution is not optimal. Consider sheep with numbers from i=1 to n

Then the final position of the $$$i-th$$$ sheep will be $$$x_m−m+i$$$, and the answer will be $$$\sum\limits_{k = 0}^n |xi−(xm−m+i)|$$$, since all the sheep have to move from $$$x_i$$$ to $$$x_m-m+i$$$.

**Code**

testcases = int(input())
for _ in range(testcases)
n = int(input())
s = input().strip()
cnt = s.count('*') # total count of sheeps
pos = -1 # hold the position of the mth sheep
cur = -1
for i in range(n):
if s[i] == '*':
cur += 1
if cur == cnt // 2:
pos = i
ans = 0
# pos -> xm cnt//2-> and i =-> 0
cur = pos - cnt // 2
for i in range(n):
if s[i] == '*':
ans += abs(cur - i)
cur += 1
print(ans)

#### E. Interesting String

**Hint 1**

Let the sum of elements from the beginning be $$$p_i$$$. $$$[l,r]$$$ is bad if the sum of all the elements between that range equals $$$r - l + 1$$$. so $$$[l,r]$$$ is bad if $$$pr−pl + 1 = r−l + 1$$$.

**Hint 2**

Rewrite the formula $$$pr−pl + 1 = r−l + 1$$$.

**Solution**

Let's precalculate the array $$$p$$$, where $$$pi=\sum\limits_{j = 0}^{i - 1} a_j$$$(so $$$p_x$$$ is the sum of the first $$$x$$$ elements of $$$a$$$). Then subarray $$$[l,r]$$$ is bad if $$$pr−pl + 1 = r−l + 1$$$, so $$$pr−r=pl−l$$$.

Thus, we have to group all prefixes by value $$$pi−i$$$ for $$$i$$$ from $$$0$$$ to $$$n$$$. And if x indexes have a prefix with the same value of $$$pi−i$$$ then we have to add $$$x(x−1)/2$$$ to the answer.

**Code**

```
from collections import defaultdict
testcases = int(input())
for _ in range(testcases):
n = int(input())
a = input()
d = defaultdict(int)
d[0] = 1
res, s = 0, 0
for i in range(n):
s += int(a[i])
x = s - i - 1
d[x] += 1
res += d[x] - 1
print(res)
```