Merge pull request halfrost#150 from ssezhangpeng/master

add leetcode_0065

Author: halfrost

leetcode/0065.Valid-Number/65. Valid Number.go

@@ -0,0 +1,23 @@
+package leetcode
+
+func isNumber(s string) bool {
+	numFlag, dotFlag, eFlag := false, false, false
+
+	for i := 0; i < len(s); i++ {
+		if '0' <= s[i] && s[i] <= '9' {
+			numFlag = true
+		} else if s[i] == '.' && !dotFlag && !eFlag {
+			dotFlag = true
+		} else if (s[i] == 'e' || s[i] == 'E') && !eFlag && numFlag {
+			eFlag = true
+			numFlag = false // reJudge integer after 'e' or 'E'
+		} else if (s[i] == '+' || s[i] == '-') && (i == 0 || s[i-1] == 'e' || s[i-1] == 'E') {
+			continue
+		} else {
+			return false
+		}
+	}
+	// avoid case: s == '.' or 'e/E' or '+/-' and etc...
+	// string s must have num
+	return numFlag
+}

leetcode/0065.Valid-Number/65. Valid Number_test.go

@@ -0,0 +1,41 @@
+package leetcode
+
+import (
+	"fmt"
+	"testing"
+)
+
+func Test_Problem65(t *testing.T) {
+
+	tcs := []struct {
+		s   string
+		ans bool
+	}{
+
+		{
+			"0",
+			true,
+		},
+
+		{
+			"e",
+			false,
+		},
+
+		{
+			".",
+			false,
+		},
+
+		{
+			".1",
+			true,
+		},
+	}
+	fmt.Printf("------------------------Leetcode Problem 65------------------------\n")
+
+	for _, tc := range tcs {
+		fmt.Printf("【input】:%v       【output】:%v\n", tc, isNumber(tc.s))
+	}
+	fmt.Printf("\n\n\n")
+}

leetcode/0065.Valid-Number/README.md

@@ -0,0 +1,49 @@
+# [65. Valid Number](https://leetcode.com/problems/valid-number/)
+
+
+## 题目
+
+A **valid number** can be split up into these components (in order):
+
+   1. A **decimal number** or an integer. 
+   2. (Optional) An 'e' or 'E', followed by an **integer.**
+   
+A **decimal number** can be split up into these components (in order):
+
+   1. (Optional) A sign character (either '+' or '-').
+   2. One of the following formats:
+        1. One or more digits, followed by a dot '.'.
+        2. One or more digits, followed by a dot '.', followed by one or more digits.
+        3. A dot '.', followed by one or more digits.
+        
+An **integer** can be split up into these components (in order):
+
+   1. (Optional) A sign character (either '+' or '-').
+   2. One or more digits.
+   
+For example, all the following are valid numbers: `["2", "0089", "-0.1", "+3.14", "4.", "-.9", "2e10", "-90E3", "3e+7", "+6e-1", "53.5e93", "-123.456e789"]`, while the following are not valid numbers: `["abc", "1a", "1e", "e3", "99e2.5", "--6", "-+3", "95a54e53"].`
+
+Given a string s, return true if s is a **valid number.**
+
+**Example:**
+
+    Input: s = "0"
+    Output: true
+    
+    Input: s = "e"
+    Output: false
+
+## 题目大意
+
+给定一个字符串S，请根据以上的规则判断该字符串是否是一个有效的数字字符串。
+
+
+## 解题思路
+
+- 用三个变量分别标记是否出现过数字、是否出现过'.'和 是否出现过 'e/E'
+- 从左到右依次遍历字符串中的每一个元素
+    - 如果是数字，则标记数字出现过
+    - 如果是 '.', 则需要 '.'没有出现过，并且 'e/E' 没有出现过，才会进行标记
+    - 如果是 'e/E', 则需要 'e/E'没有出现过，并且前面出现过数字，才会进行标记
+    - 如果是 '+/-', 则需要是第一个字符，或者前一个字符是 'e/E'，才会进行标记，并重置数字出现的标识
+    - 最后返回时，需要字符串中至少出现过数字，避免下列case: s == '.' or 'e/E' or '+/e' and etc...