solve problem String To Integer Atoi

Author: P-ppc

README.md

@@ -307,6 +307,7 @@ All solutions will be accepted!
 |789|[Escape The Ghosts](https://leetcode-cn.com/problems/escape-the-ghosts/description/)|[java/py/js](./algorithms/EscapeTheGhosts)|Medium|
 |701|[Insert Into A Binary Search Tree](https://leetcode-cn.com/problems/insert-into-a-binary-search-tree/description/)|[java/py/js](./algorithms/InsertIntoABinarySearchTree)|Medium|
 |165|[Compare Version Numbers](https://leetcode-cn.com/problems/compare-version-numbers/description/)|[java/py/js](./algorithms/CompareVersionNumbers)|Medium|
+|8|[String To Integer Atoi](https://leetcode-cn.com/problems/string-to-integer-atoi/description/)|[java/py/js](./algorithms/StringToIntegerAtoi)|Medium|
 
 # Database
 |#|Title|Solution|Difficulty|

algorithms/StringToIntegerAtoi/README.md

@@ -0,0 +1,2 @@
+# String To Integer Atoi
+This problem is easy to solve

algorithms/StringToIntegerAtoi/Solution.java

@@ -0,0 +1,38 @@
+class Solution {
+    public int myAtoi(String str) {
+        str = str.trim();
+        if (str.length() == 0)
+            return 0;
+        
+        int val = 0,
+            i = 1;
+        boolean isNegative = false;
+        
+        char prefix = str.charAt(0);
+        if (prefix == '+' || prefix == '-')
+            isNegative = prefix == '-' ? true : false;
+        else if (Character.isDigit(prefix))
+            val = prefix - '0';
+        else
+            return 0;
+        
+        int maxInt = 2147483647,
+            minInt = -2147483648,
+            spInt = 214748364;
+        
+        while (i < str.length() && Character.isDigit(str.charAt(i))) {
+            int v = str.charAt(i++) - '0';
+            if (val > spInt)
+                return isNegative ? minInt : maxInt;
+            else if (val == spInt) {
+                if (isNegative && v > 8)
+                    return minInt;
+                else if (!isNegative && v > 7)
+                    return maxInt;
+            }
+            val = val * 10 + v;
+        }
+        
+        return isNegative ? -val : val;
+    }
+}

algorithms/StringToIntegerAtoi/solution.js

@@ -0,0 +1,39 @@
+/**
+ * @param {string} str
+ * @return {number}
+ */
+var myAtoi = function(str) {
+    str = str.trim()
+    if (str.length == 0)
+        return 0
+    
+    let val = 0,
+        isNegative = false,
+        i = 1
+    
+    if (str[0] == '+' || str[0] == '-')
+        isNegative = str[0] == '-' ? true : false
+    else if ('0' <= str[0] && str[0] <= '9')
+        val = str[0] - 0
+    else
+        return 0
+    
+    let maxInt = 2147483647,
+        minInt = -2147483648,
+        spInt = 214748364
+    
+    while (i < str.length && '0' <= str[i] && str[i] <= '9') {
+        let v = str[i++] - 0
+        if (val > spInt)
+            return isNegative ? minInt : maxInt
+        else if (val == spInt) {
+            if (isNegative && v > 8)
+                return minInt
+            else if (!isNegative && v > 7)
+                return maxInt
+        }
+        val = val * 10 + v
+    }
+    
+    return isNegative ? -val : val
+};

algorithms/StringToIntegerAtoi/solution.py

@@ -0,0 +1,39 @@
+class Solution(object):
+    def myAtoi(self, str):
+        """
+        :type str: str
+        :rtype: int
+        """
+        s = str.strip()
+        if len(s) == 0:
+            return 0
+        
+        val = 0
+        is_negative = False
+        i = 1
+        
+        if s[0] == '+' or s[0] == '-':
+            is_negative = False if s[0] == '+' else True
+        elif s[0].isdigit():
+            val = ord(s[0]) - 48
+        else:
+            return 0
+            
+        max_int = 2147483647
+        min_int = -2147483648
+        special_int = 214748364
+        
+        while i < len(s) and s[i].isdigit():
+            v = ord(s[i]) - 48
+            if val > special_int:
+                return min_int if is_negative else max_int
+            elif val == special_int:
+                if is_negative and v > 8:
+                    return min_int
+                elif not is_negative and v > 7:
+                    return max_int
+            val = val * 10 + v
+            i += 1
+        
+        return -val if is_negative else val
+