排列问题

剑指 Offer 38. 字符串的排列

var permutation = function(s) {
    let n = s.length;
    if (n <= 1) {
        return [s];
    }
    let ans = [s[0]];
    for (let i = 1; i < n; i++) {
        ans = ans.map(a => getInserts(a, s[i]));
        ans = ans.flat(); // flat 返回新数组
    }
    // ans 需要去重
    return Array.from(new Set(ans));
};
function getInserts(target, intertChar) {
    let ans = [];
    let n = target.length;
    for (let i = 0; i <= n; i++) {
        let arr = target.split('');
        arr.splice(i, 0, intertChar); 
        let tmp = arr.join('');
        ans.push(tmp);
    }
    return ans;
}
permutation('ABC');