73 lines
1.7 KiB
Java
73 lines
1.7 KiB
Java
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import edu.princeton.cs.introcs.StdIn;
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import edu.princeton.cs.introcs.StdOut;
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/***********************************************************************************
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* Compilation: javac LSD.java
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* Execution: java LSD < input.txt
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*
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* LSD radix sort an array of extended ASCII strings, each of length W.
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*
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* % java LSD < words3.txt
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* all
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* bad
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* bed
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* bug
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* dad
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* ...
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* yes
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* yet
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* zoo
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*
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***********************************************************************************/
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public class LSD {
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// LSD radix sort
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public static void sort(String[] a, int W) {
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int N = a.length;
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int R = 256; // extend ASCII alphabet size
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String[] aux = new String[N];
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for (int d = W-1; d >= 0; d--) {
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// sort by key-indexed counting on dth character
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// compute frequency counts
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int[] count = new int[R+1];
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for (int i = 0; i < N; i++)
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count[a[i].charAt(d) + 1]++;
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// compute cumulates
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for (int r = 0; r < R; r++)
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count[r+1] += count[r];
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// move data
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for (int i = 0; i < N; i++)
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aux[count[a[i].charAt(d)]++] = a[i];
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// copy back
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for (int i = 0; i < N; i++)
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a[i] = aux[i];
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}
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}
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public static void main(String[] args) {
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String[] a = StdIn.readAllStrings();
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int N = a.length;
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// check that strings have fixed length
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int W = a[0].length();
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for (int i = 0; i < N; i++)
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assert a[i].length() == W : "Strings must have fixed length";
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// sort the strings
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sort(a, W);
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// print results
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for (int i = 0; i < N; i++)
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StdOut.println(a[i]);
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}
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}
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