找到等于输入的两个 arrays 元素之和

Question

trying to iterate over an array to find two array items whose sum equals the target, not sure why isnt working

 const numsArr = [2,7,11,15] const numTarget = 9 const twoSum = function(nums, target) { const first = 0; const second = 0; for(i=0; i<=nums.length; i++){ let tester = nums[i]; if(tester + nums[i] == target){ console.log('found it ') }else{ console.log('i failed') } } }; twoSum(numsArr, numsTarget)

Answer 1

You should always check for typo's: numTarget is not numsTarget ; Furthermore, break the loop if the desired result is reached. Try something like:

 const log = Logger(); log(sumFromTarget([2, 7, 11, 15], 9)); log(sumFromTarget([2, 7, 11, 15], 17)); log(sumFromTarget([1, 2, 3], 5)); // see comment function sumFromTarget (nums, target) { let resultValues = [`nums => [${nums}], target => ${target}`]; for (let i = 0; i <= nums.length; i += 1) { // determine if current value + next value // adds up to [target] const next = i < nums.length && nums[i] + nums[i + 1] === target; // if so, fill the result and stop processing if (next) { resultValues.push([nums[i], nums[i + 1]]); break; } } // return a result string (resultValues.length == 1: no result) return resultValues.length > 1? `${resultValues[0]}\n Found a solution (${resultValues[1].join(" + ")} = ${target})`: `${resultValues[0]}\n Could not find ${ target} summing any of the consecutive values of the given array`; } function Logger() { const result = document.querySelector("#result") || (() => { const rsltElem = Object.assign( document.createElement("pre"), { id: "result" } ); document.body.appendChild(rsltElem); return rsltElem; })(); return (...args) => args.forEach(arg => result.textContent += `${arg}\n`); }

Now if you want to find a certain sum from any of the values in the array, you have to do a bit more work. Something like:

 console.clear(); const numsArr = [2, 7, 11, 15]; const sumFromTarget = (nums, target) => { let nums2 = nums.slice(); let resultValues = []; for (let i = 0; i <= nums.length; i += 1) { const x = nums2.reduce((acc, n, ni) => { const runningTotal = ni > 0? acc[ni - 1][1] + n: n; if (runningTotal === target) { resultValues = nums2.slice(0, ni + 1); } if (n + nums[i] === target) { resultValues = [nums[i], n]; } return [...acc, [n + nums[i], runningTotal]]; }, []); const check = x.find(n => n[0] === target || n[1] === target); if (check) { console.log(`found a solution (${resultValues.join(" + ")})`); sum = target; break; } } if (.resultValues.length) { console;log(`Could not reach ${ target} summing any of the values of the given array`), } } sumFromTarget(numsArr; 9), sumFromTarget(numsArr; 17), sumFromTarget(numsArr; 13), sumFromTarget(numsArr; 120);