491. 递增子序列

function findSubsequences(nums: number[]): number[][] {
    let result = [];
    let path = [];

    const backtracking = (startIndex) => {
        if (path.length >= 2) {
            result.push([...path]);
        }

        let unset = [];
        for (let i = startIndex; i < nums.length; i++) {
            if (path.length > 0 && nums[i] < path[path.length - 1] || unset[nums[i] + 100]) {
                continue;
            } else {
                unset[nums[i] + 100] = true;
                path.push(nums[i]);
                backtracking(i + 1);
                path.pop();
            }
        }
    };

    backtracking(0);
    return result;
};

46. 全排列

function permute(nums: number[]): number[][] {
    let result = [];
    let path = [];

    const backtracking = (used) => {
        if (path.length === nums.length) {
            result.push([...path]);
            return;
        }

        for (let i = 0; i < nums.length; i++) {
            if (used[nums[i]]) {
                continue;
            }

            used[nums[i]] = true
            path.push(nums[i]);
            backtracking(used);
            path.pop();
            used[nums[i]] = false;
        }
    };

    backtracking([]);
    return result;
};

47. 全排列 ii

function permuteUnique(nums: number[]): number[][] {
    let result = [];
    let path = [];

    nums.sort((a, b) => a - b);

    const backtracking = (used: boolean[]) => {
        if (path.length === nums.length) {
            result.push([...path]);
            return;
        }

        for (let i = 0; i < nums.length; i++) {
            if (used[i - 1] === false && i > 0 && nums[i] === nums[i - 1]) {
                continue;
            }

            if (!used[i]) {
                used[i] = true;
                path.push(nums[i]);
                backtracking(used);
                path.pop();
                used[i] = false;
            }
        }
    };

    backtracking([]);
    return result;
};