Compare two version numbers version1 and version2.
If version1 > version2 return 1, if version1 < version2 return -1, otherwise return 0.
You may assume that the version strings are non-empty and contain only digits and the . character.
The . character does not represent a decimal point and is used to separate number sequences.
For instance, 2.5 is not "two and a half" or "half way to version three", it is the fifth second-level revision of the second first-level revision.
Here is an example of version numbers ordering:
0.1 < 1.1 < 1.2 < 13.37
比较两个字符串数字的大小：（小数点可能不止一个）
注意的地方：
1、多个小数点的处理。
2、考虑清楚细节就可以了，题目本身不难。
1、直接判断，代码较多。
public class Solution {
public int compareVersion(String version1, String version2) {
int len1 = version1.length();
int len2 = version2.length();
int start1 = 0;
int start2 = 0;
int[] nums = new int[2];
while (start1 < len1 && start2 < len2){
nums = getNum(version1, start1, len1);
int num1 = nums[1];
start1 = nums[0];
nums = getNum(version2, start2, len2);
int num2 = nums[1];
start2 = nums[0];
if (num1 > num2){
return 1;
} else if (num1 < num2){
return -1;
}
}
if (start1 >= len1 && start1 >= len2){
return 0;
} else if (start1 >= len1){
while (start2 < len2){
nums = getNum(version2, start2, len2);
if (nums[1] != 0){
return -1;
}
start2 = nums[0];
}
return 0;
} else {
while (start1 < len1){
nums = getNum(version1, start1, len1);
if (nums[1] != 0){
return 1;
}
start1 = nums[0];
}
return 0;
}
}
public int[] getNum(String str, int start, int len){
int end = start;
int[] result = new int[2];
while (end < len && str.charAt(end) != '.'){
end++;
}
result[0] = end+1;
if( end == start){
result[1] = 0;
} else {
result[1] = Integer.valueOf(str.substring(start,end));
}
return result;
}
}
2、同样的处理方式，也有很简单的写法（参考discuss）
public class Solution {
public int compareVersion(String version1, String version2) {
int temp1 = 0,temp2 = 0;
int len1 = version1.length(),len2 = version2.length();
int i = 0,j = 0;
while(i<len1 || j<len2) {
temp1 = 0;
temp2 = 0;
while(i<len1 && version1.charAt(i) != '.') {
temp1 = temp1*10 + version1.charAt(i++)-'0';
}
while(j<len2 && version2.charAt(j) != '.') {
temp2 = temp2*10 + version2.charAt(j++)-'0';
}
if(temp1>temp2) return 1;
else if(temp1<temp2) return -1;
else {
i++;
j++;
}
}
return 0;
}
}
3、使用split（）。（参考discuss）
public int compareVersion(String version1, String version2) {
String[] v1 = version1.split("\\.");
String[] v2 = version2.split("\\.");
for ( int i = 0; i < Math.max(v1.length, v2.length); i++ ) {
int num1 = i < v1.length ? Integer.parseInt( v1[i] ) : 0;
int num2 = i < v2.length ? Integer.parseInt( v2[i] ) : 0;
if ( num1 < num2 ) {
return -1;
} else if ( num1 > num2 ) {
return +1;
}
}
return 0;
}