Участник:StasFomin/Solutions/codechef/CCDSAP

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• Codechef/CCDSAP

# from future import print_function,division
# range = xrange
import sys
input = sys.stdin.readline
from sys import stdin, stdout
from math import ceil
import heapq 
 
def main(): # n^2 approach
    for _ in range(int(input())):
        n = int(input())
        s = input().strip()
        if n==1:
            print(0)
            continue
        m = s.count("1")
        j = 1
        pos = [-1]*(m+1)
        for i in range(n):
            if s[i]=="1":
                pos[j] = i+1
                j+=1
            if j>m:
                break
        dp = [[[10**9+7,10**9+7] for i in range(m+1)] for j in range(n+1)]
        for i in range(n+1):
            for j in range(m+1):
                for filled in range(2):
                    if j==0:
                        dp[i][j][filled] = 0
                        continue
                    if j > ceil(i/2):
                        continue
                    if filled==1:
                        dp[i][j][filled] = dp[i-1][j-1][0] + abs(pos[j]-i)
                    else:
                        a = dp[i-1][j][0]
                        b = dp[i-1][j][1]
                        dp[i][j][filled] = min(a,b)
        ans = min(dp[n][m][0], dp[n][m][1])
        if ans==10**9+7:
            print("impossible")
        else:
            print(ans)
 
def main1(): # NlogN approach (Slope Trick)
    for _ in range(int(input())):
        n = int(input())
        s = input().strip()
        if n==1:
            print(0)
            continue
        m = s.count("1")
        if m==0:
            print(0)
            continue
        if m> (n+1)//2:
            print("impossible")
            continue
        j = 0
        pos = [-1]*(m)
        for i in range(n):
            if s[i]=="1":
                pos[j] = i
                j+=1
        heap = [0]*(m+4)
        maxopt = n+1-2*m
        curropt = -10
        ans = 0
        for i in range(m):
            if -heap[0]<= pos[i]-2*i:
                curropt = min(maxopt, pos[i])
                heapq.heappush(heap, -(curropt-2*i))
            else:
                heapq.heappush(heap, -(pos[i]-2*i))
                curropt = -heap[0]+2*i
                heapq.heappop(heap)
                heapq.heappush(heap, -(pos[i]-2*i))
            ans += abs(curropt - pos[i])
            maxopt+=2
        print(ans)
 
 
 
if __name__ == "__main__":
    # main()
    main1()