#8. String to Integer (atoi)

Author: YugenCoder

MyAtoI.java

@@ -0,0 +1,45 @@
+package leetcode;
+
+import java.util.Arrays;
+import java.util.List;
+
+public class MyAtoI {
+
+	public static void main(String[] args) {
+		MyAtoI atoi = new MyAtoI();
+		int res = atoi.convertAtoI("-2147483647");
+		System.out.println(res);
+		// Test for negatives
+		// Test for positives
+		// Test for invalid Entries
+	}
+
+	public int convertAtoI(String str) {
+	    int baseValue = 0;
+		int sign = 1, idx = 0;
+		
+        // skip spaces
+        while (idx < str.length() && str.charAt(idx) == ' ') {
+			idx++;
+		}
+         
+        // check sign    
+		if (idx < str.length() && (str.charAt(idx) == '-' || str.charAt(idx) == '+')) {
+			sign = str.charAt(idx++) == '+' ? 1 : -1;
+		}
+            
+        // calculate integer           
+		while (idx < str.length()) {
+			int digit = str.charAt(idx) - '0';
+			if (digit >= 0 && digit <= 9) {
+				if ((baseValue  + digit*0.1)  > (Integer.MAX_VALUE/10 + (Integer.MAX_VALUE%10)*0.1)) {
+					return (sign == 1) ? Integer.MAX_VALUE : Integer.MIN_VALUE;
+				}
+				baseValue = baseValue * 10 + digit;
+			} else 
+				break;
+			idx++;
+		}
+		return sign * baseValue;
+	}
+}