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# Program to find number of subsequences with i, j and k number of x, y, z letters in Python

Suppose we have a string s with "x", "y" and "z"s, we have to find the number of subsequences that have i number of "x" characters, followed by j number of "y" characters and followed by k number of "z" characters where i, j, k ≥ 1.

So, if the input is like s = "xxyz", then the output will be 3, as we can make two "xyz" and one "xxyz"

To solve this, we will follow these steps:

n := size of s

x := 0, y := 0, z := 0

for i in range 0 to n, do

count := 0

if s[i] is same as "x", then

x := x * 2

x := x + 1

if s[i] is same as "y", then

y := y * 2

y := y + x

if s[i] is same as "z", then

z := z * 2

z := z + y

return z

## Example

class Solution: def solve(self, s): n = len(s) x = 0 y = 0 z = 0 for i in range(n): count = 0 if s[i] == "x": x *= 2 x += 1 if s[i] == "y": y *= 2 y += x if s[i] == "z": z *= 2 z += y return z ob = Solution() print(ob.solve("xxyz"))

## Input

"xxyz"

## Output

3

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