378 adding

Author: aQua

Algorithms/0378.kth-smallest-element-in-a-sorted-matrix/README.md

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+# [378. Kth Smallest Element in a Sorted Matrix](https://leetcode.com/problems/kth-smallest-element-in-a-sorted-matrix/)
+
+## 题目
+
+Given a n x n matrix where each of the rows and columns are sorted in ascending order, find the kth smallest element in the matrix.
+
+Note that it is the kth smallest element in the sorted order, not the kth distinct element.
+
+```text
+Example:
+matrix = [
+   [ 1,  5,  9],
+   [10, 11, 13],
+   [12, 13, 15]
+],
+k = 8,
+
+return 13.
+```
+
+Note:
+You may assume k is always valid, 1 ≤ k ≤ n2.
+
+## 解题思路
+
+见程序注释

Algorithms/0378.kth-smallest-element-in-a-sorted-matrix/kth-smallest-element-in-a-sorted-matrix.go

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+package Problem0378
+
+func kthSmallest(mat [][]int, k int) int {
+	if len(mat) == 0 || len(mat[0]) == 0 {
+		return 0
+	}
+
+	m, n := len(mat), len(mat[0])
+
+	return res
+}

Algorithms/0378.kth-smallest-element-in-a-sorted-matrix/kth-smallest-element-in-a-sorted-matrix_test.go

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+package Problem0378
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+var mat = [][]int{
+	[]int{1, 5, 9},
+	[]int{10, 11, 13},
+	[]int{12, 13, 15},
+}
+
+// tcs is testcase slice
+var tcs = []struct {
+	k   int
+	ans int
+}{
+
+	{8, 13},
+
+	// 可以有多个 testcase
+}
+
+func Test_kthSmallest(t *testing.T) {
+	ast := assert.New(t)
+
+	for _, tc := range tcs {
+		fmt.Printf("~~%v~~\n", tc)
+		ast.Equal(tc.ans, kthSmallest(mat, tc.k), "输入:%v", tc)
+	}
+}
+
+func Benchmark_kthSmallest(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range tcs {
+			kthSmallest(tc.matrix, tc.k)
+		}
+	}
+}