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Input: Hello World Output: dlroW olleH
Input: Hi Ram! Output: Reversed: !maR iH
1. Program to Reverse a string
Pseudo Algorithm
- Use a temp variable result that stores reversed string. Initialize it with empty string.
- Iterate given string from end index to start start.
- For each position, get the string at that index and append it in string result
- Terminate the loop when we reach to start index.
- Finally, value present in result variable is reversed string.
Sourcecode –
fun main() { println("Enter string:") val str = readLine() var result: String = "" var lastIndex = str!!.lastIndex while (lastIndex >= 0) { result += str[lastIndex] lastIndex-- } println("Reversed: $result") }
When you run the program, output will be –
Enter string: Hello Rahul! How are you? Reversed: ?uoy era woH !luhaR olleH
Explanation:
- Read the value entered by user using readLine() function.
Then, store this value in variable str - Then, define a variable, result that stores the reversed string.
- Then, get the last index of the string and store it in variable lastIndex.
We do this to get position of the last character present in string. - Then, run a while loop from last index, lastIndex, of the string.
- Append each character present at index
lastIndex in variable result. - Then, decrease the value of lastIndex by 1.
- Repeat the loop till we reach at first character in string.
Let’s take an example,
Assume user entered
string = “hello”
Now,
result = “”
lastIndex = 4
run a loop from 4 till lastIndex becomes 0
-
After iteration at lastIndex = 4,
result = “o”
lastIndex = 3 -
After iteration at lastIndex = 3,
result = “ol”
lastIndex = 2 -
After iteration at lastIndex = 2,
result = “oll”
lastIndex = 1 -
After iteration at lastIndex = 1,
result = “olle”
lastIndex = 0 -
After iteration at lastIndex = 0,
result = “olleh”
lastIndex = -1
Value at variable result is reversed of variable str.
Thus, we went through Kotlin Program to Reverse a given string.
Similarly, you can use this kotlin program to reverse a sentence.
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