把字符串转换成整数

include/jianzhi_offer.h

@@ -44,6 +44,15 @@ public:
      * @return
      */
     std::string reverse_left_words(std::string s, int n);
+
+    /**
+     * 剑指 Offer 67. 把字符串转换成整数
+     *
+     * @url   https://leetcode.cn/leetbook/read/illustration-of-algorithm/58pq8g/
+     * @param str
+     * @return
+     */
+    int str_to_int(std::string str);
 };
 
 class ListNode {
@@ -72,10 +81,9 @@ public:
     * @return
     */
     ListNode *reverse_list(ListNode *head);
-    ListNode* reverse_list(ListNode* cur, ListNode* pre);
+    ListNode *reverse_list(ListNode *cur, ListNode *pre);
 };
 
-
 class Node {
 public:
     int val;
@@ -95,7 +103,7 @@ public:
      * @param head
      * @return
      */
-    Node* copy_random_list(Node* head);
+    Node *copy_random_list(Node *head);
 };
 
 /**
@@ -123,6 +131,5 @@ private:
  * @param k
  * @return
  */
-std::vector<int> max_sliding_window(std::vector<int>& nums, int k);
-
+std::vector<int> max_sliding_window(std::vector<int> &nums, int k);
 }

src/jianzhi_offer/string.cpp

@@ -45,4 +45,22 @@ bool String::is_number(std::string s) {
 
     return false;
 }
+
+int String::str_to_int(std::string str) {
+    int res = 0, bndry = INT_MAX/10;
+    int i = 0, sign = 1, length = str.size();
+    if (length == 0) return 0;
+    while (str[i] == ' ')
+        if (++i == length) return 0;
+    if (str[i] == '-') sign = -1;
+    if (str[i] == '-' || str[i] == '+') i++;
+    for (int j = i; j < length; j++) {
+        if (str[j] < '0' || str[j] > '9') break;
+        if (res > bndry || res == bndry && str[j] > '7')
+            return sign == 1 ? INT_MAX : INT_MIN;
+        res = res*10 + (str[j] - '0');
+    }
+    return sign*res;
+}
+
 }

tests/jianzhi_offer/string_test.cpp

@@ -18,9 +18,17 @@ TEST(IsNumberTest, BasicAssertions) {
     ASSERT_FALSE(s.is_number("e9"));
 }
 
-TEST(ReverseLeftWords, BasicAssertions) {
+TEST(ReverseLeftWordsTest, BasicAssertions) {
     yaha::String s;
     ASSERT_EQ("cdefgab", s.reverse_left_words("abcdefg", 2));
     ASSERT_EQ("umghlrlose", s.reverse_left_words("lrloseumgh", 6));
 }
 
+TEST(StringToIntTest, BasicAssertions) {
+    yaha::String s;
+    ASSERT_EQ(42, s.str_to_int("42"));
+    ASSERT_EQ(-42, s.str_to_int("-42"));
+    ASSERT_EQ(-42, s.str_to_int(" -42"));
+    ASSERT_EQ(4193, s.str_to_int("4193 with words"));
+    ASSERT_EQ(0, s.str_to_int("words and 987"));
+}