Added task 8.

Author: javadev

src/main/java/s0008.string.to.integer.atoi/Solution.java

@@ -0,0 +1,43 @@
+package s0008.string.to.integer.atoi;
+
+public class Solution {
+    public int myAtoi(String str) {
+        if (str == null || str.length() == 0)
+            return 0;
+
+        int i = 0;
+        boolean negetiveSign = false;
+        char[] input = str.toCharArray();
+
+        while (i < input.length && input[i] == ' ') {
+            i++;  
+        }
+
+        if (i == input.length) {
+            return 0;
+        } else if (input[i] == '+') {
+            i++;
+        } else if (input[i] == '-') {
+            i++;
+            negetiveSign = true;
+        }
+
+        int num = 0;
+        while (i < input.length && input[i] <= '9' && input[i] >= '0') {
+            int tem = input[i] - '0';  //current char
+            tem = negetiveSign ? -tem : tem;
+
+            if (num == 0 && tem == '0') { // avoid invalid number like 038
+                i++;
+            } else if (num == Integer.MIN_VALUE / 10 && tem <= -8 || num < Integer.MIN_VALUE / 10) {
+                return Integer.MIN_VALUE;
+            } else if (num == Integer.MAX_VALUE / 10 && tem >= 7 || num > Integer.MAX_VALUE / 10) {
+                return Integer.MAX_VALUE;
+            } else {
+                num = num * 10 + tem;
+                i++;
+            }
+        }
+        return num;
+    }
+}

src/test/java/s0008.string.to.integer.atoi/SolutionTest.java

@@ -0,0 +1,12 @@
+package s0008.string.to.integer.atoi;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+import org.junit.Test;
+
+public class SolutionTest {
+    @Test
+    public void myAtoi() {
+        assertThat(new Solution().myAtoi("42"), equalTo(42));
+    }
+}