Merge pull request #889 from 0xff-dev/1404

Add solution and test-cases for problem 1404

Author: 6boris

leetcode/1401-1500/1404.Number-of-Steps-to-Reduce-a-Number-in-Binary-Representation-to-One/README.md

@@ -0,0 +1,47 @@
+# [1404.Number of Steps to Reduce a Number in Binary Representation to One][title]
+
+## Description
+Given the binary representation of an integer as a string `s`, return the number of steps to reduce it to `1` under the following rules:
+
+- If the current number is even, you have to divide it by `2`.
+
+- If the current number is odd, you have to add `1` to it.
+
+It is guaranteed that you can always reach one for all test cases.
+
+**Example 1:**
+
+```
+Input: s = "1101"
+Output: 6
+Explanation: "1101" corressponds to number 13 in their decimal representation.
+Step 1) 13 is odd, add 1 and obtain 14. 
+Step 2) 14 is even, divide by 2 and obtain 7.
+Step 3) 7 is odd, add 1 and obtain 8.
+Step 4) 8 is even, divide by 2 and obtain 4.  
+Step 5) 4 is even, divide by 2 and obtain 2. 
+Step 6) 2 is even, divide by 2 and obtain 1.
+```
+
+**Example 2:**
+
+```
+Input: s = "10"
+Output: 1
+Explanation: "10" corressponds to number 2 in their decimal representation.
+Step 1) 2 is even, divide by 2 and obtain 1.
+```
+
+**Example 3:**
+
+```
+Input: s = "1"
+Output: 0
+```
+
+## 结语
+
+如果你同我一样热爱数据结构、算法、LeetCode，可以关注我 GitHub 上的 LeetCode 题解：[awesome-golang-algorithm][me]
+
+[title]: https://leetcode.com/problems/number-of-steps-to-reduce-a-number-in-binary-representation-to-one
+[me]: https://github.com/kylesliu/awesome-golang-algorithm

leetcode/1401-1500/1404.Number-of-Steps-to-Reduce-a-Number-in-Binary-Representation-to-One/Solution.go

@@ -1,5 +1,26 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+func Solution(s string) int {
+	bs := []byte(s)
+	steps := 0
+	idx := len(s) - 1
+	for idx >= 0 {
+		if string(bs[:idx+1]) == "1" {
+			break
+		}
+		if bs[idx] == '0' {
+			idx--
+			steps++
+			continue
+		}
+		steps += 1
+		for ; idx >= 0 && bs[idx] != '0'; idx-- {
+			steps++
+		}
+		if idx >= 0 {
+			bs[idx] = '1'
+		}
+	}
+
+	return steps
 }

leetcode/1401-1500/1404.Number-of-Steps-to-Reduce-a-Number-in-Binary-Representation-to-One/Solution_test.go

@@ -10,12 +10,12 @@ func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
 		name   string
-		inputs bool
-		expect bool
+		inputs string
+		expect int
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", "1101", 6},
+		{"TestCase2", "10", 1},
+		{"TestCase3", "1", 0},
 	}
 
 	//	开始测试
@@ -30,10 +30,10 @@ func TestSolution(t *testing.T) {
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }