日常积累几个算法,帮助理解数据结构和Java语言。
<1>问题描述
SOURCE : LeetCode(28)
Implement strStr().
Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.
Example 1:
Input: haystack = "hello", needle = "ll"
Output: 2
Example 2:
Input: haystack = "aaaaa", needle = "bba"
Output: -1
A nsw er:
class Solution {
public int strStr(String haystack, String needle) {
if(haystack.equals("") && needle.equals(""))
return 0;
if(needle.equals(""))
return 0;
if(haystack.equals(""))
return -1;
for(int i = 0; i <= haystack.length()-needle.length(); i++){
int j = 0;
for(; j < needle.length(); j++){
if(haystack.charAt(i+j) != needle.charAt(j))
break;
}
if(j == needle.length())
return i;
}
return -1;
}
}
<2>问题描述
SOURCE : LeetCode(1)
Given an array of integers, return indices of the two numbers such that they add up to a specific target.
You may assume that each input would have exactly one solution, and you may not use the same element twice.
Example:
Given nums = [2, 7, 11, 15], target = 9,
Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].
Answer:
class Solution {
public int[] twoSum(int[] nums, int target) {
int num = 0;
int[] result = new int[2];
for(int i = 0; i < nums.length; i++){
for(int j = i+1; j<nums.length; j++){
num = nums[i]+nums[j];
if(num == target){
result[0] = i;
result[1] = j;
}
}
}
return result;
}
}