diff --git a/240. Search a 2D Matrix II/README.org b/240. Search a 2D Matrix II/README.org
new file mode 100644
index 0000000..646b0e5
--- /dev/null
+++ b/240. Search a 2D Matrix II/README.org	
@@ -0,0 +1,14 @@
+#+TITLE: 240. Search a 2D Matrix II
+x,y 方向都递增的二维数组中找一个数。在剑指 offer 上做过。
+* 文件及解法说明
+** [[./sample_20ms_submission.go][20ms 示例解法]]
+别人的。时间复杂度 O(mlogn)。
+
+** [[./search_a_2d_matrix_ii.go][我的解法]]
+O(m+n)
+
+** 递归
+midx, midy := (top+right)/2, (left+right)/2
+若 matrix[midx][midy]<target, target 不可能在左上。接下来搜索右上，左下，右下；
+若 matrix[midx][midy]>target, target 不可能在右下。
+
diff --git a/240. Search a 2D Matrix II/sample_20ms_submission.go b/240. Search a 2D Matrix II/sample_20ms_submission.go
new file mode 100644
index 0000000..c28ee92
--- /dev/null
+++ b/240. Search a 2D Matrix II/sample_20ms_submission.go	
@@ -0,0 +1,27 @@
+func searchMatrix(matrix [][]int, target int) bool {
+	for i := 0; i < len(matrix); i++ {
+		if binsearch(matrix[i], target) {
+			return true
+		}
+	}
+
+	return false
+}
+
+func binsearch(arr []int, target int) bool {
+	hi := len(arr) - 1
+	lo := 0
+
+	for lo <= hi {
+		mid := (lo + hi) / 2
+		if arr[mid] == target {
+			return true
+		} else if arr[mid] < target {
+			lo = mid + 1
+		} else {
+			hi = mid - 1
+		}
+	}
+
+	return false
+}
\ No newline at end of file
diff --git a/240. Search a 2D Matrix II/search_a_2d_matrix_ii.go b/240. Search a 2D Matrix II/search_a_2d_matrix_ii.go
new file mode 100644
index 0000000..2e95dd5
--- /dev/null
+++ b/240. Search a 2D Matrix II/search_a_2d_matrix_ii.go	
@@ -0,0 +1,18 @@
+package leetcode
+
+func searchMatrix(matrix [][]int, target int) bool {
+	if len(matrix) == 0 {
+		return false
+	}
+	x, y := 0, len(matrix[0])-1
+	for x < len(matrix) && y >= 0 {
+		if matrix[x][y] > target {
+			y--
+		} else if matrix[x][y] < target {
+			x++
+		} else {
+			return true
+		}
+	}
+	return false
+}