PROBLEM DESCRIPTION
Given a character array s, reverse the order of the words. A word is defined as a sequence of non-space characters. The words in s will be separated by a single space. Your code must solve the problem in-place, i.e. without allocating extra space.
SOLUTION
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class Solution {
public void reverseWords(char[] s) {
int n = s.length;
// Step 1: Reverse the entire character array
reverseRange(s, 0, n-1);
// Initialize pointers i and j for word reversal
int i=0;
int j=0;
// Step 2: Iterate through the character array to reverse individual words
while(i<n){
// Move the j pointer to the end of the current word
while(j<n && s[j] != ' '){
j++;
}
// Step 3: Reverse the current word (from i to j-1)
reverseRange(s, i, j-1);
// Move the i and j pointers to the next word
i = j + 1;
j++;
}
}
// Helper function to reverse a range of characters in the array
public void reverseRange(char[] s, int i, int j){
while(i<j){
// Swap characters at positions i and j
char t = s[i];
s[i] = s[j];
s[j] = t;
// Move the pointers towards each other
i++;
j--;
}
}
}