add solution of problem 74: search a 2D matrix

Author: ppulse

SearchA2DMatrix74/README.md

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+Write an efficient algorithm that searches for a value in an *m* x *n* matrix. This matrix has the following properties:
+
+- Integers in each row are sorted from left to right.
+- The first integer of each row is greater than the last integer of the previous row.
+For example,
+
+Consider the following matrix:
+```
+[
+  [1,   3,  5,  7],
+  [10, 11, 16, 20],
+  [23, 30, 34, 50]
+]
+```
+Given **target** = `3`, return `true`.

SearchA2DMatrix74/Solution.java

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+public class Solution {
+    public boolean searchMatrix(int[][] matrix, int target) {
+        if (matrix == null || matrix.length == 0 || matrix[0].length == 0)
+            return false;
+        
+        int rowIdx = 0;
+        int colsNum = matrix[0].length;
+        int rowsNum = matrix.length;
+        
+        while (rowIdx < rowsNum && matrix[rowIdx][colsNum - 1] < target)
+            rowIdx++;
+        
+        if (rowIdx == rowsNum)
+            return false;
+        
+        int left = 0;
+        int right = colsNum - 1;
+        
+        while (left <= right) {
+            int mid = (left + right) >> 1;
+            if (matrix[rowIdx][mid] < target)
+                left = mid + 1;
+            else if (matrix[rowIdx][mid] > target)
+                right = mid - 1;
+            else
+                return true;
+        }
+        
+        return false;
+    }
+}