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179. Largest Number

Description

Given a list of non-negative integers nums, arrange them such that they form the largest number and return it.

Since the result may be very large, so you need to return a string instead of an integer.

 

Example 1:

Input: nums = [10,2]
Output: "210"

Example 2:

Input: nums = [3,30,34,5,9]
Output: "9534330"

 

Constraints:

  • 1 <= nums.length <= 100
  • 0 <= nums[i] <= 109

Solutions

Solution 1

Thinking

Form the largest number by concatenation. Numeric order and plain lexicographic order both fail: \(9\) should precede \(98\) because \(998>989\). \(n\le 100\). Compare \(a+b\) with \(b+a\) to order two strings, sort by that, and join. If the first character is \(0\), every value was zero, so return \(\texttt{"0"}\).

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class Solution:
    def largestNumber(self, nums: List[int]) -> str:
        nums = [str(v) for v in nums]
        nums.sort(key=cmp_to_key(lambda a, b: 1 if a + b < b + a else -1))
        return "0" if nums[0] == "0" else "".join(nums)

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class Solution {
    public String largestNumber(int[] nums) {
        List<String> vs = new ArrayList<>();
        for (int v : nums) {
            vs.add(v + "");
        }
        vs.sort((a, b) -> (b + a).compareTo(a + b));
        if ("0".equals(vs.get(0))) {
            return "0";
        }
        return String.join("", vs);
    }
}

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class Solution {
public:
    string largestNumber(vector<int>& nums) {
        vector<string> vs;
        for (int v : nums) vs.push_back(to_string(v));
        sort(vs.begin(), vs.end(), [](string& a, string& b) {
            return a + b > b + a;
        });
        if (vs[0] == "0") return "0";
        string ans;
        for (string v : vs) ans += v;
        return ans;
    }
};

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func largestNumber(nums []int) string {
    vs := make([]string, len(nums))
    for i, v := range nums {
        vs[i] = strconv.Itoa(v)
    }
    sort.Slice(vs, func(i, j int) bool {
        return vs[i]+vs[j] > vs[j]+vs[i]
    })
    if vs[0] == "0" {
        return "0"
    }
    return strings.Join(vs, "")
}

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public class Comparer: IComparer<string> {
    public int Compare(string left, string right) {
        return Compare(left, right, 0, 0);
    }

    private int Compare(string left, string right, int lBegin, int rBegin) {
        var len = Math.Min(left.Length - lBegin, right.Length - rBegin);
        for (var i = 0; i < len; ++i) {
            if (left[lBegin + i] != right[rBegin + i]) {
                return left[lBegin + i] < right[rBegin + i] ? -1 : 1;
            }
        }

        if (left.Length - lBegin == right.Length - rBegin) {
            return 0;
        }
        if (left.Length - lBegin > right.Length - rBegin) {
            return Compare(left, right, lBegin + len, rBegin);
        }
        else {
            return Compare(left, right, lBegin, rBegin + len);
        }
    }
}

public class Solution {
    public string LargestNumber(int[] nums) {
        var sb = new StringBuilder();
        var strs = nums.Select(n => n.ToString(CultureInfo.InvariantCulture)).OrderByDescending(s => s, new Comparer());

        var nonZeroOccurred = false;
        foreach (var str in strs) {
            if (!nonZeroOccurred && str == "0") continue;
            sb.Append(str);
            nonZeroOccurred = true;
        }
        return sb.Length == 0 ? "0" : sb.ToString();
    }
}

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function largestNumber(nums: number[]): string {
    nums.sort((a, b) => {
        const [ab, ba] = [String(a) + String(b), String(b) + String(a)];
        return +ba - +ab;
    });

    return nums[0] ? nums.join('') : '0';
}

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function largestNumber(nums) {
    nums.sort((a, b) => {
        const [ab, ba] = [String(a) + String(b), String(b) + String(a)];
        return +ba - +ab;
    });

    return nums[0] ? nums.join('') : '0';
}

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