uploading class code

Author: Algorithmica

2018-feb/adhoc-thinking/src/com/alg/top20/adhoc/FindDuplicate.java

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+package com.alg.top20.adhoc;
+import java.util.Arrays;
+
+public class FindDuplicate {
+
+	// pair wise check
+	public static int findDuplicate1(int[] in) {
+		for (int i = 0; i < in.length - 1; ++i) {
+			for (int j = i + 1; j < in.length; ++j) {
+				if (in[i] == in[j])
+					return in[i];
+			}
+		}
+		return -1;
+	}
+	
+	// sort + scan
+	public static int findDuplicate2(int[] in) {
+		Arrays.sort(in);
+		for (int i = 1; i < in.length; ++i) {
+			if(in[i] == in[i-1]) return in[i];
+		}
+		return -1;
+	}
+	
+	// in-place check
+	public static int findDuplicate4(int[] in) {
+		int element = -1;
+		for (int i = 0; i < in.length; ++i) {
+			element = Math.abs(in[i]);
+			if(in[element] < 0) break;				
+			in[element] *= -1;
+		}
+		//System.out.println(Arrays.toString(in));
+		return element;
+	}
+
+	public static void main(String[] args) {
+		int n = Integer.parseInt(args[0]);
+		int[] in = new int[n];
+		//testcase1
+		int i;
+		for(i = 0; i < in.length-1; ++i)
+			in[i] = i+1;
+		in[i] = i;
+		//System.out.println(Arrays.toString(in));
+		long start = System.currentTimeMillis();
+		System.out.println(findDuplicate4(in));
+		long end = System.currentTimeMillis();
+		System.out.println("Time:" + (end-start)/1000.0 +"seconds");
+	}
+
+}

2018-feb/adhoc-thinking/src/com/alg/top20/adhoc/MatrixSearch.java

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+package com.alg.top20.adhoc;
+
+import java.util.Arrays;
+
+public class MatrixSearch {
+
+	// binary search on each row
+	public static boolean matrixSearch1(int[][] in, int target) {
+		int m = in.length;
+		for (int i = 0; i < m; ++i) {
+			if (Arrays.binarySearch(in[i], target) >= 0)
+				return true;
+		}
+		return false;
+	}
+
+	// find the required row by linear search
+	// along last column
+	// binary search on that row
+	public static boolean matrixSearch2(int[][] in, int target) {
+		int m = in.length;
+		int n = in[0].length;
+		int i;
+		for (i = 0; i < m; ++i) {
+			if (target <= in[i][n - 1])
+				break;
+		}
+		return Arrays.binarySearch(in[i], target) >= 0;
+	}
+
+	public static boolean matrixSearch3(int[][] in, int target) {
+		int m = in.length;
+		int n = in[0].length;
+
+		int left = 0, right = n * m - 1;
+
+		while (left <= right) {
+			int mid = (left + right) / 2;
+			int element = in[mid / n][mid % n];
+			if (element == target)
+				return true;
+			if (target < element)
+				right = mid - 1;
+			else
+				left = mid + 1;
+		}
+		return false;
+	}
+
+	public static void main(String[] args) {
+		
+		
+
+	}
+
+}