[js] 选择数组中两数和与目标值对相等，优化算法提升效率

#

            //timeout
            var sum_pairs1 = function(ints, s) {
                    var l = ints.length,
                        temp = [],
                        least = 10000000;
                    for (var i = 0; i < l - 1; i++) {
                        for (var j = i + 1; j < l; j++) {
                            if (ints[i] + ints[j] == s && j - i < least) {
                                least = j - i;
                                temp[0] = ints[i];
                                temp[1] = ints[j];
                            }
                        }
                    }
                    if (temp.length > 0) {
                        return temp;
                    } else {
                        return undefined;
                    }
                }
                //hash
            var sum_pairs2 = function(ints, s) {
                    var seen = {}
                    for (var i = 0; i < ints.length; ++i) {
                        //console.info(s,ints[i],s-ints[i]);
                        if (seen[s - ints[i]]) {
                            return [s - ints[i], ints[i]];
                        }
                        seen[ints[i]] = true
                            //console.log(seen);
                    }
                }
                //利用 while 、 break、indexOf
            var sum_pairs3 = function(ints, s) {
                    var i = 0;
                    var tried = [];
                    var pairIndex1 = [];
                    var pairIndex2 = [];
                    var arrayLen = ints.length;
                    while (i < arrayLen) {
                        if (tried.indexOf(ints[i]) === -1) {
                            for (var j = i + 1; j < arrayLen; j++) {
                                if (ints[i] + ints[j] === s) {
                                    pairIndex1.push(i);
                                    pairIndex2.push(j);
                                    break;
                                }
                            }
                            tried.push(ints[i]);
                            //console.info(tried);
                        }
                        i++;
                    }
                    //console.log(pairIndex1, pairIndex2);
                    if (pairIndex1.length === 0) {
                        return undefined;
                    } else if (pairIndex1.length === 1) {
                        return [ints[pairIndex1[0]], ints[pairIndex2[0]]];
                    } else {
                        var lowestIndexInInts = Math.min.apply(null, pairIndex2);
                        var posInPairs = pairIndex2.indexOf(lowestIndexInInts);
                        return [ints[pairIndex1[posInPairs]], ints[lowestIndexInInts]];
                    }
                }
                //不稳定的写法
            var sum_pairs4 = function(ints, s) {
                ints = remove_duplicates(ints);
                //console.log(ints);
                for (var i = 1; i < ints.length; i++) {
                    for (var j = 0; j < i; j++) {
                        if (ints[j] + ints[i] === s) {
                            return [ints[j], ints[i]];
                        }
                    }
                }
                return undefined;
            };
            var remove_duplicates = function(ints) {
                //去重
                return ints.reduce(function(acc, current) {
                    if (acc.length === 0 || acc[acc.length - 1] !== current) {
                        acc.push(current);
                        return acc;
                    } else {
                        return acc;
                    }
                }, []);
            };
            //other
            var sum_pairs = function(ints, s) {
                var res = [ints.length, ints.length];
                var maps = [];
                for (var i = 0; i < ints.length; i++) {
                    if (maps[s - ints[i]]) {
                        return [s - ints[i], ints[i]];
                    }
                    maps[ints[i]] = [i];
                    //console.log(maps);
                }
            }


            l1 = [1, 4, 8, 7, 3, 15];
            l2 = [1, -2, 3, 0, -6, 1];
            l3 = [20, -13, 40];
            l4 = [1, 2, 3, 4, 1, 0];
            l5 = [10, 5, 2, 3, 7, 5];
            l6 = [4, -2, 3, 3, 4];
            l7 = [0, 2, 0];
            l8 = [5, 9, 13, -3];
            sum_pairs(l1, 8);
            sum_pairs(l2, -6);
            sum_pairs(l3, -7);
            sum_pairs(l4, 2);
            sum_pairs(l5, 10);
            sum_pairs(l6, 8);
            sum_pairs(l7, 0);
            sum_pairs(l8, 10);

 

```

function sum_pairs(ints, s) {
  let seen = new Set();
  for (let i of ints) {
    if (seen.has(s - i)) return [s - i, i];
    seen.add(i);
  }
}

```