Merge pull request algorithm-visualizer#202 from archie94/majority-vote-problem

Majority Vote Problem

Author: TornjV

algorithm/category.json

@@ -46,7 +46,8 @@
    },
    "greedy": {
       "list": {
-         "job_scheduling": "Job Scheduling Problem"
+         "job_scheduling": "Job Scheduling Problem",
+         "majority_element": "Majority Element(Boyer–Moore majority vote algorithm)"
       },
       "name": "Greedy"
    },

algorithm/greedy/majority_element/basic/code.js

@@ -0,0 +1,63 @@
+function isMajorityElement ( element ) {
+	var count = 0;
+	logger._print ('Verify majority element ' + element );
+	for (var i = N - 1; i >= 0; i--) {
+		tracer._notify (i,A[i])._wait ();
+		if (A[i] == element) {
+			count++;
+		} else {
+			tracer._denotify (i);
+		}
+	}
+	logger._print ('Count of our assumed majority element ' + count);
+	if(count>Math.floor (N/2)) {
+		logger._print ('Our assumption was correct!');
+		return true;
+	}
+	logger._print ('Our assumption was incorrect!');
+	return false;
+}
+
+function findProbableElement () {
+	var index = 0, count = 1;
+	tracer._select (index)._wait();
+	logger._print ('Beginning with assumed majority element : ' + A[index] + ' count : ' +count);
+	logger._print ('--------------------------------------------------------');
+	for( var i = 1; i < N; i++ ) {
+		tracer._notify (i,A[i])._wait ();
+		if(A[index]==A[i]) {
+			count++;
+			logger._print ('Same as assumed majority element! Count : ' + count);
+		} else {
+			count--;
+			logger._print ('Not same as assumed majority element! Count : ' + count);
+		}
+
+		if(count===0) {
+			logger._print ('Wrong assumption in majority element');
+			tracer._deselect (index);
+			tracer._denotify (i);
+			index = i;
+			count = 1;
+			tracer._select (i)._wait ();
+			logger._print ('New assumed majority element!'+ A[i]  +' Count : '+count);
+			logger._print ('--------------------------------------------------------');
+		} else {
+			tracer._denotify (i);		
+		}
+	}
+	logger._print ('Finally assumed majority element ' + A[index]);
+	logger._print ('--------------------------------------------------------');
+	return A[index];
+}
+
+function findMajorityElement () {
+	var element = findProbableElement ();
+	if(isMajorityElement (element) === true) {
+		logger._print ('Majority element is ' + element);
+	} else {
+		logger._print ('No majority element');
+	}
+}
+
+findMajorityElement ();

algorithm/greedy/majority_element/basic/data.js

@@ -0,0 +1,5 @@
+var A = [ 1, 3, 3, 2, 1, 1, 1 ];
+var N = A.length;
+
+var tracer = new Array1DTracer('List of element')._setData (A);
+var logger = new LogTracer ('Console');

algorithm/greedy/majority_element/desc.json

@@ -0,0 +1,13 @@
+{
+  "Majority Element(Boyer–Moore majority vote algorithm)": "The majority vote problem is to determine in any given sequence of choices whether there is a choice with more occurrences than half of the total number of choices in the sequence and if so, to determine this choice.",
+  "Complexity": {
+    "time": " O(N)",
+    "space": "O(logN)"
+  },
+  "References": [
+    "<a href='https://en.wikipedia.org/wiki/Boyer%E2%80%93Moore_majority_vote_algorithm'>Wikipedia</a>"
+  ],
+  "files": {
+    "basic": "Find majority element in array using Boyer–Moore majority vote algorithm"
+  }
+}