Suppose we have a binary string, we have to find the minimum number of swaps needed to group all 1’s together in any place in the string. So if the input is like "10101001101", then the output will be 3, as possible solution is "00000111111".
To solve this, we will follow these steps −
data := a list of bits from the given string
set one := 0, n:= length of data array
make an array summ of size n, and fill this with 0, set summ[0] := data[0]
one := one + data[0]
for i in range 1 to n – 1
summ[i] := summ[i - 1] + data[i]
one := one + data[i]
ans := one
left := 0, right := one – 1
while right < n
if left is 0, then temp := summ[right], otherwise temp := summ[right] –
- summ[left - 1]
ans := minimum of ans, one – temp
increase right and left by 1
return ans
Let us see the following implementation to get better understanding −
Example
class Solution(object):
def solve(self, data):
data = list(map(int, list(data)))
one = 0
n = len(data)
summ=[0 for i in range(n)]
summ[0] = data[0]
one += data[0]
for i in range(1,n):
summ[i] += summ[i-1]+data[i]
one += data[i]
ans = one
left = 0
right = one-1
while right <n:
if left == 0:
temp = summ[right]
else:
temp = summ[right] - summ[left-1]
ans = min(ans,one-temp)
right+=1
left+=1
return ans
ob = Solution()
print(ob.solve("10101001101"))Input
"10101001101"
Output
3