字符串转换整数（提交成功代码）

MouCoder · MouCoder · commit 4dfce58a70ce · 2020-08-17T21:52:02.000+08:00
diff --git a/stringToInt/Solution.java b/stringToInt/Solution.java
@@ -0,0 +1,41 @@
+package LeetCode.String.stringToInt;
+
+public class Solution {
+    public int myAtoi(String str) {
+        double num = 0;
+        for(int i = 0;i < str.length();i++) {
+            //判断第一个非空格字符是否为数字或者'-'
+            if (str.charAt(i) != ' ' && ((str.charAt(i) == '-' || str.charAt(i) == '+')|| (str.codePointAt(i) >= 48 && str.codePointAt(i) <= 57))) {
+                //如果第一个非空格字符是'-'但是'-'后不是数字，直接返回0
+                if (i<str.length()-1&&str.charAt(i) == '-' && (str.codePointAt(i+1) < 48 || str.codePointAt(i+1) > 57)) {
+                    num = 0;
+                    break;
+                }
+                else if (str.charAt(i) == '-') {
+                    for (int j = i + 1; j < str.length() && (str.codePointAt(j) >= 48 && str.codePointAt(j) <= 57); j++) {
+                        num = (num * 10 + Integer.parseInt(str.substring(j,j+1)));
+                    }
+                    num = (-1) * num;
+                    break;
+                }else if (i<str.length()-1&&str.charAt(i) == '+' && (str.codePointAt(i+1) < 48 || str.codePointAt(i+1) > 57)) {
+                    num = 0;
+                    break;
+                }else if(str.charAt(i) == '+'){
+                    for (int j = i+1;j < str.length() && (str.codePointAt(j) >= 48 && str.codePointAt(j) <= 57) ; j++) {
+                        num = (num * 10 + Integer.parseInt(str.substring(j,j+1)));
+                    }
+                    break;
+                }else{
+                    for (int j = i;j < str.length() && (str.codePointAt(j) >= 48 && str.codePointAt(j) <= 57) ; j++) {
+                        num = (num * 10 + Integer.parseInt(str.substring(j,j+1)));
+                    }
+                    break;
+                }
+            } else if (str.charAt(i) != ' '){
+                num = 0;
+                break;
+            }
+        }
+        return (int)num;
+    }
+}
diff --git a/stringToInt/Test.java b/stringToInt/Test.java
@@ -0,0 +1,8 @@
+package LeetCode.String.stringToInt;
+
+public class Test {
+    public static void main(String[] args) {
+        Solution sol = new Solution();
+        System.out.println(sol.myAtoi("42"));
+    }
+}
diff --git a/stringToInt/stringToInt/Solution.java b/stringToInt/stringToInt/Solution.java
@@ -0,0 +1,41 @@
+package LeetCode.String.stringToInt;
+
+public class Solution {
+    public int myAtoi(String str) {
+        double num = 0;
+        for(int i = 0;i < str.length();i++) {
+            //判断第一个非空格字符是否为数字或者'-'
+            if (str.charAt(i) != ' ' && ((str.charAt(i) == '-' || str.charAt(i) == '+')|| (str.codePointAt(i) >= 48 && str.codePointAt(i) <= 57))) {
+                //如果第一个非空格字符是'-'但是'-'后不是数字，直接返回0
+                if (i<str.length()-1&&str.charAt(i) == '-' && (str.codePointAt(i+1) < 48 || str.codePointAt(i+1) > 57)) {
+                    num = 0;
+                    break;
+                }
+                else if (str.charAt(i) == '-') {
+                    for (int j = i + 1; j < str.length() && (str.codePointAt(j) >= 48 && str.codePointAt(j) <= 57); j++) {
+                        num = (num * 10 + Integer.parseInt(str.substring(j,j+1)));
+                    }
+                    num = (-1) * num;
+                    break;
+                }else if (i<str.length()-1&&str.charAt(i) == '+' && (str.codePointAt(i+1) < 48 || str.codePointAt(i+1) > 57)) {
+                    num = 0;
+                    break;
+                }else if(str.charAt(i) == '+'){
+                    for (int j = i+1;j < str.length() && (str.codePointAt(j) >= 48 && str.codePointAt(j) <= 57) ; j++) {
+                        num = (num * 10 + Integer.parseInt(str.substring(j,j+1)));
+                    }
+                    break;
+                }else{
+                    for (int j = i;j < str.length() && (str.codePointAt(j) >= 48 && str.codePointAt(j) <= 57) ; j++) {
+                        num = (num * 10 + Integer.parseInt(str.substring(j,j+1)));
+                    }
+                    break;
+                }
+            } else if (str.charAt(i) != ' '){
+                num = 0;
+                break;
+            }
+        }
+        return (int)num;
+    }
+}
diff --git a/stringToInt/stringToInt/Test.java b/stringToInt/stringToInt/Test.java
@@ -0,0 +1,8 @@
+package LeetCode.String.stringToInt;
+
+public class Test {
+    public static void main(String[] args) {
+        Solution sol = new Solution();
+        System.out.println(sol.myAtoi("42"));
+    }
+}
