leetcode

JavaStudy/src/com/algorithm/leetcode/Sub8_StringtoInteger.java

@@ -0,0 +1,69 @@
+package com.algorithm.leetcode;
+
+public class Sub8_StringtoInteger {
+	public int myAtoi(String str) {
+		str = str.trim();
+		int pre = 1;
+		int index = 0;
+		int preNum = 0;
+		if (str == null || str.equals("")) {
+			return 0;
+		}
+		long result = 0;
+		if (str.charAt(index) == '-') {
+			pre = -1;
+			preNum++;
+			index++;
+		} else {
+			if (str.charAt(index) == '+') {
+				pre = 1;
+				preNum++;
+				index++;
+			} else {
+				if (str.charAt(index) > '9' || str.charAt(index) < '0')
+					return 0;
+			}
+		}
+
+		if (index >= str.length() || preNum > 1) {
+			return 0;
+		}
+
+		for (int i = index; i < str.length(); i++) {
+			if (str.charAt(i) >= '0' && str.charAt(i) <= '9') {
+				if(i>12){
+					result = 2147483648L;
+					break;
+				}
+				result = result * 10 + str.charAt(i) - '0';
+			} else {
+				break;
+			}
+
+		}
+
+		if (result >= 2147483647 && pre == 1) {
+			return Integer.MAX_VALUE;
+		}
+		if (result >= 2147483648L && pre == -1) {
+			return Integer.MIN_VALUE;
+		}
+		result = result * pre;
+		return (int) result;
+	}
+
+	public static void main(String[] args) {
+		Sub8_StringtoInteger sub = new Sub8_StringtoInteger();
+		// System.out.println(Integer.valueOf("  -0012a42"));
+		System.out.println(sub.myAtoi("1111"));
+		System.out.println(sub.myAtoi("+-2"));
+		System.out.println(sub.myAtoi("+"));
+		System.out.println(sub.myAtoi("2147483647"));
+		int i = 2147483647;
+		i++;
+		System.out.println(Integer.MAX_VALUE);
+		System.out.println(Integer.MIN_VALUE);
+		System.out.println(sub.myAtoi("2147483648"));
+		System.out.println(sub.myAtoi("9223372036854775809"));
+	}
+}