力扣----1.两数之和(JavaScript, Java实现)

实现原理一样，时间复杂度O(n)

JavaScript实现

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number[]}
 */
var twoSum = function(nums, target) {
    let tempMap= new Map()
    for(let i = 0; i < nums.length; i++){
        let numOther = target - nums[i]
        if (tempMap.has(numOther)) {
        　　return [tempMap.get(numOther), i]
        }
        tempMap.set(nums[i], i)
    }
};

Java实现

class Solution {
    public int[] twoSum(int[] nums, int target) {
        Map<Integer, Integer> tempMap = new HashMap<>();
        for(int i=0; i<nums.length;i++){
            int numOther = target - nums[i];
            if(tempMap.containsKey(numOther)){
                return new int[] {tempMap.get(target- nums[i]), i};
            }
            tempMap.put(nums[i], i);           
        }
        throw new IllegalArgumentException("none") ;
    }
}