88 lines
2.6 KiB
Java
88 lines
2.6 KiB
Java
package cd.test;
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// NOTE: This code was adapted from the code found at
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// http://www.cs.princeton.edu/introcs/96optimization/Diff.java.html
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/*************************************************************************
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* Compilation: javac Diff
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* Execution: java Diff filename1 filename2
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* Dependencies: In.java
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*
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* Reads in two files and compute their diff.
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* A bare bones version.
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*
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* % java Diff input1.txt input2.txt
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*
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*
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* Limitations
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* -----------
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* - Could hash the lines to avoid potentially more expensive
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* string comparisons.
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*
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*************************************************************************/
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public class Diff {
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public static String computeDiff(String in0, String in1) {
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StringBuffer out = new StringBuffer();
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// break into lines of each file
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String[] x = in0.split("\\n");
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String[] y = in1.split("\\n");
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// number of lines of each file
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int M = x.length;
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int N = y.length;
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// opt[i][j] = length of LCS of x[i..M] and y[j..N]
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int[][] opt = new int[M+1][N+1];
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// compute length of LCS and all subproblems via dynamic programming
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for (int i = M-1; i >= 0; i--) {
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for (int j = N-1; j >= 0; j--) {
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if (x[i].equals(y[j]))
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opt[i][j] = opt[i+1][j+1] + 1;
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else
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opt[i][j] = Math.max(opt[i+1][j], opt[i][j+1]);
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}
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}
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// recover LCS itself and print out non-matching lines to standard output
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boolean lineNumber = false;
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int i = 0, j = 0;
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while(i < M && j < N) {
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if (x[i].equals(y[j])) {
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i++;
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j++;
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lineNumber = false;
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}
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else {
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if (!lineNumber) {
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out.append(String.format(
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"At line %3d / %3d:\n", i+1, j+1));
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lineNumber = true;
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}
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assert lineNumber;
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if (opt[i+1][j] >= opt[i][j+1])
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out.append("< " + x[i++] + "\n");
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else
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out.append("> " + y[j++] + "\n");
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}
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}
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// dump out one remainder of one string if the other is exhausted
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if (!lineNumber) {
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out.append(String.format("Line %3d / %3d:\n", i+1, j+1));
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}
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while(i < M || j < N) {
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if (i == M)
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out.append("> " + y[j++] + "\n");
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else if (j == N)
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out.append("< " + x[i++] + "\n");
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}
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return out.toString();
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}
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}
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