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duaraghav8@gmail
committed
Knuth Morris Pratt
1 parent 99719a7 commit f6d7864

5 files changed

Lines changed: 153 additions & 3 deletions

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‎algorithm/category.json‎

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"string": {
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"name": "String",
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"list": {
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"edit_distance": "Edit Distance"
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"edit_distance": "Edit Distance",
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"knuth_morris_pratt": "KMP Substring Search"
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}
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},
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"dp": {

‎algorithm/graph_search/bridges/desc.json‎

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{
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"Bridges": "An edge in an undirected connected graph is a bridge iff removing it disconnects the graph. A naive solution to finding bridges in a graph is to:<br />1.Delete an edge E<br />2.Perform DFS Exploration to check is Graph is connected<br />3.Restore Edge E. E is a bridge only if DFS explore determines that the graph is disconnected without E",
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"Bridges": "An edge in an undirected connected graph is a bridge iff removing it disconnects the graph. A naive solution to finding bridges in a graph is to:<br />1.Delete an edge E<br />2.Perform DFS Exploration to check if the Graph is still connected<br />3.Restore Edge E. E is a bridge only if DFS exploration determines that the graph is disconnected without E",
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"Applications": [
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"Find vulnerabilities in Graphs and Electrical Circuits"
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"Finding vulnerabilities in Graphs and Electrical Circuits"
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],
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"Complexity": {
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"time": "worst O(|E|.(|V|+|E|))",

‎algorithm/string/knuth_morris_pratt/desc.json‎

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{
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"Knuth-Morris-Pratt": "searches for occurrences of a substring W with length K within a main string S with Length N by employing the observation that when a mismatch occurs, the word itself embodies sufficient information to determine where the next match could begin, thus bypassing re-examination of previously matched characters",
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"Applications": [
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"Substring Search"
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],
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"Complexity": {
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"time": "worst O(|N|+|K|)",
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"space": "worst O(|K|)"
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},
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"References": [
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"<a href='https://en.wikipedia.org/wiki/Knuth%E2%80%93Morris%E2%80%93Pratt_algorithm'>Wikipedia</a>"
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],
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"files": {
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"substring_search": "Efficiently find is A is a substring of B (and A's position(s))"
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}
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}

‎algorithm/string/knuth_morris_pratt/substring_search/code.js‎

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//Fix JS Negative number modulo Bug
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Number.prototype.mod = function (n) {
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return ((this%n)+n)%n;
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};
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function randString (length) {
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var result = Math.random ().toString (36);
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return result.substring (result.length - length);
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}
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function tracker (substring) {
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var i = 1, j = 0;
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logger._print ('Initializing i to 1, j to 0.');
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substrTracer._select (j);
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while (i < track.length) {
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substrTracer._select (i)._wait ();
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while ( (substring [i] !== substring [j]) && (j > 0) ) {
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logger._print ('j = ' + track [j-1]);
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trackTracer._select (j-1)._wait ();
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trackTracer._deselect (j-1)._wait ();
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substrTracer._deselect (j);
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j = track [j-1];
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logger._print ('j = ' + j);
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substrTracer._select (j);
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}
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if (substring [i] === substring [j]) {
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substrTracer._deselect (j);
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track [i] = ++j;
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trackTracer._notify (i, track [i])._wait ();
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trackTracer._denotify (i)._wait ();
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logger._print ('substring [ ' + i + ' ] (' + substring [i] + ') equals substring [ ' + j + ' ] (' + substring [j] + '), track [ ' + i + ' ] updated to: ' + track [i]);
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logger._print ('j = ' + j);
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substrTracer._select (j);
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}
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else {
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track [i] = 0;
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logger._print ('substring [ ' + i + ' ] (' + substring [i] + ') is not equal to substring [ ' + j + ' ] (' + substring [j] + '), setting track [' + i + '] to 0');
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trackTracer._select (i)._wait ();
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trackTracer._deselect (i)._wait ();
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}
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substrTracer._deselect (i)._wait ();
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i++;
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logger._print ('i = ' + i);
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}
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return track;
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}
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function kmp (string, substr) {
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var positions = [], j = 0, startPos;
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logger._print ('Constructing Tracker for substring <b>' + substr + '</b>');
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track = tracker (substr);
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logger._print ('Tracker for substring constructed: [ ' + String (track) + ' ]');
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logger._print ('--------------------------------------------------------------------------');
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logger._print ('Running KMP...');
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logger._print ('Initializing i = 0, j = 0');
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for (var i = 0; i < string.length; i++) {
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logger._print ('comparing string [' + i + '] (' + string [i] + ') and substring [' + j + '] (' + substr [j] + ')...');
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stringTracer._select (i)._wait ();
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stringTracer._select (j)._wait ();
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if (string [i] === substr [j]) {
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logger._print ('they\'re equal!');
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if (j === substr.length-1) {
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logger._print ('j (' + j + ') equals length of substring - 1 (' + substr.length + '-1), we\'ve found a new match in the string!');
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startPos = i - substr.length + 1;
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positions.push (startPos);
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logger._print ('Adding start position of the substring (' + startPos + ') to the results.');
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stringTracer._select (startPos)._wait ();
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}
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else {
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stringTracer._deselect (j)._wait ();
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logger._print ('But j (' + j + ') does not equal length of substring (' + substr.length + ') Incrementing j and moving forward.');
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j++;
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logger._print ('j = ' + j);
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stringTracer._select (j)._wait ();
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}
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}
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else {
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var tempJ = j - 1;
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logger._print ('they\'re NOT equal');
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trackTracer._select (tempJ)._wait ();
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stringTracer._deselect (j)._wait ();
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j = track [(j-1).mod (substr.length)]; //use modulo to wrap around, i.e., if index = -1, access the LAST element of array (PYTHON-LIKE)
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logger._print ('Setting j to ' + j);
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stringTracer._select (j)._wait ();
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trackTracer._deselect (tempJ)._wait ();
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}
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stringTracer._deselect (i)._wait ();
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}
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return positions;
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}
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var positions = kmp (string, substring);
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logger._print ('Substring positions are: ' + (positions.length ? String (positions) : 'NONE'));
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for (var i = 0; i < positions.length; i++) {
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stringTracer._select (positions [i], positions [i] + substring.length - 1)._wait ();
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}

‎algorithm/string/knuth_morris_pratt/substring_search/data.js‎

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function randString (length) {
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var result = Math.random ().toString (36);
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return result.substring (result.length - length);
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}
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var string = randString (15), substring = randString (5);
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//var string = 'abcxabcdabxabcdabcdabxabcda', substring = 'xabcda';
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//var string = 'abcxabcdabxabcdabcdabcyiuhsiuhduiahdubhbuuabcdabcysbhbh', substring = 'abcdabcy';
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var track = Array.apply (null, Array (substring.length)).map (Number.prototype.valueOf, 0);
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var logger = new LogTracer ();
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var trackTracer = new Array1DTracer (),
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substrTracer = new Array1DTracer (),
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stringTracer = new Array1DTracer ();
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trackTracer._setData (track);
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substrTracer._setData (substring);
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stringTracer._setData (string);

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