#8 字符串转换成整数

Isaaclot · Isaaclot · commit 81267c57f5fa · 2020-04-03T07:36:01.000+08:00
diff --git a/main/src/array/LC_8_StringToIntegerAtoi.java b/main/src/array/LC_8_StringToIntegerAtoi.java
@@ -0,0 +1,30 @@
+package array;
+
+/**
+ * @author liangqian0723@gmail.com
+ * @since 2020/4/3 6:58 AM
+ */
+public class LC_8_StringToIntegerAtoi {
+    public int myAtoi(String str) {
+        if (null == str || str.length() == 0) return 0;
+        char[] array = str.toCharArray();
+        int res = 0;
+        int curIndex = 0;
+        int flag = 1;
+        while (array[curIndex] == ' ') {
+            curIndex++;
+            if (curIndex >= str.length()) return 0;
+        }
+        if (array[curIndex] == '-') flag = -1;
+        if (array[curIndex] == '+' || array[curIndex] == '-') curIndex++;
+        while (curIndex < str.length() && Character.isDigit(array[curIndex])) {
+            int r = array[curIndex] - '0';
+            if (res > (Integer.MAX_VALUE - r) / 10 || res < Integer.MIN_VALUE / 10) {
+                return flag > 0 ? Integer.MAX_VALUE : Integer.MIN_VALUE;
+            }
+            res = res * 10 + r;
+            curIndex++;
+        }
+        return flag > 0 ? res : res * flag;
+    }
+}
diff --git a/main/test/array/LC_8_StringToIntegerAtoiTest.java b/main/test/array/LC_8_StringToIntegerAtoiTest.java
@@ -0,0 +1,22 @@
+package array;
+
+import org.junit.Test;
+
+import static org.hamcrest.core.Is.is;
+import static org.junit.Assert.assertThat;
+
+/**
+ * @author liangqian0723@gmail.com
+ * @since 2020/4/3 6:56 AM
+ */
+public class LC_8_StringToIntegerAtoiTest {
+    @Test
+    public void test_string_to_integer_atomic() {
+        LC_8_StringToIntegerAtoi at = new LC_8_StringToIntegerAtoi();
+        assertThat(at.myAtoi("   -42"), is(-42));
+        assertThat(at.myAtoi("4193 with words"), is(4193));
+        assertThat(at.myAtoi("words and 987"), is(0));
+        assertThat(at.myAtoi("  "), is(0));
+        assertThat(at.myAtoi("2147483648"), is(2147483647));
+    }
+}
