1. 两数之和-https://leetcode-cn.com/problems/two-sum/

[AmelloAster]

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number[]}
 */
var twoSum = function(nums, target) {
        let org = [...nums]
        let copy = [...nums]
        let result = []
        var counts = {};
        copy.forEach(function(x, index) { counts[x] = index; })
        for(let [index, num] of nums.entries()) {
            let ends = org.splice(0, 1)
            let newArr = [num, ...org]
            newArr.reduce((x, y) => {
                if ( x + y === target) {
                    result = [index, counts[y]]
                }
                return x;
            })
        }
        return result
};

[zhaojianing]

/**

• @param {number[]} nums
• @param {number} target
• @return {number[]} */

var twoSum = function(nums, target) { let indexAry = []; for (let i = 0;i < nums.length; i++) { let dataI = nums[i]; if (i === nums.length - 1) { continue; } for (let j = i+1; j < nums.length; j++) { let dataJ = nums[j]; if (dataI + dataJ === target) { indexAry[0] = i; indexAry[1] = j; } } } return indexAry; };

let nums = [2, 7, 11, 15]; let target = 9; twoSum(nums,target);

[tailgo]

// 暴力解法 A，156 ms | 34.7 MB
var twoSum = function (nums, target) {
    for (var i = 0; i < nums.length - 1; ++i) {
        for (var j = i + 1; j < nums.length; ++j) {
            if (nums[i] + nums[j] == target) {
                return [i, j];
            }
        }
    }
}

// 还是没有骚成功的解法 B，124ms | 38.6MB
var twoSum = function (nums, target) {
    var maps = {};
    for (var i = 0; i < nums.length; ++i) {
        if (typeof maps[nums[i]] !== 'undefined') {
            maps[nums[i]].push(i);
        } else {
            maps[nums[i]] = [i];
        }
    }
    nums = nums.sort(function (a, b) { return a - b > 0 ? 1 : -1; })
    for (var i = 0; i < nums.length - 1; ++i) {

        for (var j = i + 1; j < nums.length; ++j) {

            if (nums[i] + nums[j] > target) {
                break;
            }

            if (nums[i] + nums[j] == target) {
                return [maps[nums[i]].shift(), maps[nums[j]].shift()];
            }

        }
    }
};

// 在解法B 的基础上优化，86ms | 36.9MB
var twoSum = function (nums, target) {
    if (nums.length == 2) return [0, 1];
    var maps = {};
    for (var i = 0; i < nums.length; ++i) {
        if (typeof maps[nums[i]] !== 'undefined') {
            maps[nums[i]].push(i);
        } else {
            maps[nums[i]] = [i];
        }
    }
    for (var i = 0; i < nums.length - 1; ++i) {
        var _t = target - nums[i];
        if (maps[_t]) {
            if (maps[_t].length == 1 && maps[_t][0] == i) continue;

            var ix = maps[nums[i]].shift();
            var iy = maps[_t].shift();
            return ix > iy ? [iy, ix] : [ix, iy];
        }
    }
};

// 一次hash出结果，最佳题解，80ms | 34.4MB
var twoSum = function (nums, target) {
    var maps = {};
    for (var i = 0; i < nums.length; ++i) {
        var t = target - nums[i];
        if (typeof maps[t] !== 'undefined') {
            return [maps[t], i];
        } else {
            maps[nums[i]] = i;
        }
    }
};