Leetcode 22: Generate Parentheses

leetcode22.ts

function generateParenthesis(n: number): string[] {
    if (n === 1) { return ["()"]; }
    
    let result = new Set<string>();
    let previousCombos = generateParenthesis(n-1);
    
    for (let i in previousCombos) {
        let combo = previousCombos[i];
        
        // wrap all previous entries in parens and put those in the set
        result.add("("+combo+")");
        
        // now step through each one and embed a new paren at each possible position
        for (let i = 0; i < combo.length; i++) {
            result.add(combo.substring(0,i) + '()' + combo.substring(i));
        }
    }
    
    return [...result];
};