leetcode-1-Two Sum

leetcode-1-Two Sum

description

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].

common method

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class Solution {
public int[] twoSum(int[] nums, int target) {
int[] ret = new int[2];
for(int i =0; i<nums.length-1 ;i++){
for (int j = i+1 ;j < nums.length ;j++ ){
if (nums[i] + nums[j] == target){
ret = new int[]{i, j};
return ret;
}
}
}
return ret ;
}
}

best method

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class Solution {
public int[] twoSum(int[] nums, int target) {
int len=nums.length;
HashMap<Integer, Integer> map=new HashMap<>();
map.put(nums[0], 0);
for(int i=1;i<len;i++){
if(map.containsKey(target-nums[i])){
int[] returnArray={map.get(target-nums[i]),i};
return returnArray;
} else{
map.put(nums[i], i);
}
}
int[] returnArray={0,0};
return returnArray;
}
}

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