LeetCode之Longest Common Prefix

1、题目

Write a function to find the longest common prefix string amongst an array of strings

2、代码实现

package leetcode.chenyu.test;

public class LongestCommonPrefix {
	public static void main(String[] args)  {
		String [] ss = {"12345", "3234", "234"};
		String [] ss1 = {"flower", "flow", "flight"};
		String [] ss2 = {"ca", "a"};
		String [] ss3 = {"a", "a"};
		String [] ss4 = {"aa","ab"};
		String [] ss5 = {"abca","aba","aaab"};
		String result =longestCommonPrefix(ss5);
		System.out.printf("result1111:" + result);
		
	}
	public static boolean isNull(String s) {
		if(s == null || s.length() == 0) {
			return true;
		}
		return false;
	} 
	public  static String longestCommonPrefix(String[] strs) {
		if(strs == null || strs.length ==0) {
			return "";
		}
		int length = strs.length;
		if (length == 1) {
			return strs[0];
		}
		int minLength = Integer.MAX_VALUE;
		int index = 0;
		for (int i = 0; i < strs.length; ++i) {
			 if (isNull(strs[i])) {
				 return "";
			 }
			 if (minLength > strs[i].length()) {
				 minLength = strs[i].length();
				 index = i;
			 }
		}
		String result = "";
		for (int i = 1; i <= minLength; ++i) {
			 int count = 0;
			 for (int j = i; j <= minLength; ++j) {
				  String s =  strs[index].substring(count++, j);
				  System.out.print("s:" + s + "\t");
				  int flag = 0;
				  for (int k = 0; k < length; k++) {
					  if (k != index) {
						  if (!strs[k].contains(s)) {
							  break;
						  } else {
							 flag++;
							 System.out.print("flag:" + flag + "\t");
							 if (flag == length - 1) {
								 if (result.length() < s.length()) {
									  int num = 0;
									  for (int h = 0; h < length; h++) {
										   if (!strs[h].startsWith(s)) {
											    break;
										   } else {
											   num++;
										   }
									  }
									  if (num == length)
									  result = s;
								 }
								 System.out.println("result:" + result + "\t");
								 break;
							 }
 						  }
					   } 
				  }
			 }
		}
		return result;
	}
}

特么一开始看错题目，虽然结果验证没有出问题，但是超时了，日了狗

下面的代码是求 字符串数组种最大的公共子串

package leetcode.chenyu.test;

public class LongestCommonPrefix {
	public static void main(String[] args)  {
		String [] ss = {"12345", "3234", "234"};
		String [] ss1 = {"flower", "flow", "flight"};
		String [] ss2 = {"ca", "a"};
		String [] ss3 = {"a", "a"};
		String [] ss4 = {"aa","ab"};
		String [] ss5 = {"abca","aba","aaab"};
		String result =longestCommonPrefix(ss5);
		System.out.printf("result1111:" + result);
		
	}
	public static boolean isNull(String s) {
		if(s == null || s.length() == 0) {
			return true;
		}
		return false;
	} 
	public  static String longestCommonPrefix(String[] strs) {
		if(strs == null || strs.length ==0) {
			return "";
		}
		int length = strs.length;
		if (length == 1) {
			return strs[0];
		}
		int minLength = Integer.MAX_VALUE;
		int index = 0;
		for (int i = 0; i < strs.length; ++i) {
			 if (isNull(strs[i])) {
				 return "";
			 }
			 if (minLength > strs[i].length()) {
				 minLength = strs[i].length();
				 index = i;
			 }
		}
		String result = "";
		for (int i = 1; i <= minLength; ++i) {
			 int count = 0;
			 for (int j = i; j <= minLength; ++j) {
				  String s =  strs[index].substring(count++, j);
				  System.out.print("s:" + s + "\t");
				  int flag = 0;
				  for (int k = 0; k < length; k++) {
					  if (k != index) {
						  if (!strs[k].contains(s)) {
							  break;
						  } else {
							 flag++;
							 System.out.print("flag:" + flag + "\t");
							 if (flag == length - 1) {
								 if (result.length() < s.length()) {
									  result = s;
								 }
								 System.out.println("result:" + result + "\t");
								 break;
							 }
 						  }
					   } 
				  }
			 }
		}
		return result;
	}
}

最后修改后可以通过LeetCode的代码

public class Solution {
    public static boolean isNull(String s) {
		if(s == null || s.length() == 0) {
			return true;
		}
		return false;
	} 
	public  static String longestCommonPrefix(String[] strs) {
		if(strs == null || strs.length ==0) {
			return "";
		}
		int length = strs.length;
		if (length == 1) {
			return strs[0];
		}
		int minLength = Integer.MAX_VALUE;
		int index = 0;
		for (int i = 0; i < strs.length; ++i) {
			 if (isNull(strs[i])) {
				 return "";
			 }
			 if (minLength > strs[i].length()) {
				 minLength = strs[i].length();
				 index = i;
			 }
		}
		String result = "";
		for (int i = 1; i <= minLength; ++i) {
			String s =  strs[index].substring(0, i);
			int flag = 0;
			for (int k = 0; k < length; k++) {
				if (k != index) {
					if (!strs[k].contains(s) || !strs[k].startsWith(s)) {
						break;
					} else {
						flag++;
					    if (flag == length - 1) {
							if (result.length() < s.length()) {
								result = s;
						}
					    break;
					   }
 				    }
			     } 
		     }
		}
		return result;
	}
}