[GeeksForGeeks] Reverse a string without using any temporary variables
阿新 • • 發佈:2017-07-22
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Given a string, reverse it without using any temporary variables.
This problem is a variation of the problem swapping two integers without using any temporary variables by XOR.
For integers x and y, to swap them using XOR, we do the following.
x = x ^ y;
y = y ^ x;
x = x ^ y;
Proof of correctness.
y = y ^ (x ^ y) = (y ^ y) ^ x = 0 ^ x = x;
x = (x ^ y) ^ x = (x ^ x) ^ y = 0 ^ y = y;
QED.
Apply this 3 steps XOR operations to each pair of characters that need to be swapped.
1 public class Solution { 2 public char[] reverseString(char[] str, int start, int end){ 3 while(start < end){4 str[start] ^= str[end]; 5 str[end] ^= str[start]; 6 str[start] ^= str[end]; 7 start++; 8 end--; 9 } 10 return str; 11 } 12 }
[GeeksForGeeks] Reverse a string without using any temporary variables