two sum
From 21:10 - 21:30array
map
My solution:
/**
* @param {number[]} nums
* @param {number} target
* @return {number[]}
*/
var twoSum = function(nums, target) {
var res = [];
// value : index
var map = {};
// tranfer arr to map
// attrieve complexity n -> 1
for(var i=0; i<nums.length; i++){
map[nums[i]] = i;
}
// assume: must have and only one solution
// looping through the arr, search the rest of value in the map
for(var j=0; j<nums.length; j++){
var rest = target - nums[j];
var index = map[rest];
if(index){
if(index!==j){
res.push(j, index);
return res;
}
}
}
};
// Time complexity: O(n)
// Runtime: 48 ms, faster than 99.85% of JavaScript online submissions for Two Sum.
// Memory Usage: 36 MB, less than 16.79% of JavaScript online submissions for Two Sum.
var twoSum = function(nums, target) {
for(let i=0;i<nums.length;i++){
for(let j=0;j<nums.length;j++){
if(i!==j&&(nums[i]+nums[j]===target)){
return [i,j];
}
}
}
};
var twoSum = function(nums, target) {
const map = {};
for(let i = 0; i < nums.length; i++) {
const currentValue = nums[i];
const wantedValue = target - currentValue;
if(map[wantedValue] !== undefined) {
return [map[wantedValue], i];
}
map[currentValue] = i;
}
};
