EASY PYTHON SOLUTION USING PREFIX SUM APPROACH ✅✅✅✅✅✅✅✅✅🔥🔥🔥🔥🔥🔥
Intuition\n Describe your first thoughts on how to solve this problem. \n\n# Approach\n Describe your approach to solving the problem. \n\n# Complexity\n- Time 
# Intuition\n<!-- Describe your first thoughts on how to solve this problem. -->\n\n# Approach\n<!-- Describe your approach to solving the problem. -->\n\n# Complexity\n- Time complexity:\n<!-- Add your time complexity here, e.g. $$O(n)$$ -->\n\n- Space complexity:\n<!-- Add your space complexity here, e.g. $$O(n)$$ -->\n\n# Code\n```\nclass Solution:\n    def shortestBeautifulSubstring(self, s: str, k: int) -> str:\n        d = {}\n        pre = 0\n        s = list(s)\n        for i in range(len(s)):\n            pre += int(s[i])\n\n            if pre not in d:\n                d[pre] = [i,i]\n            else:\n                if i > d[pre][1] :\n                    d[pre][1] = i\n\n        res = []\n\n       \n                \n        for i in d:\n            if i == k:\n                res.append(int("".join(s[0:d[i][0]+1])))\n            if i - k in d:\n                res.append(int("".join(s[d[i-k][1]+ 1 : d[i][0]+1])))\n        \n        \n\n        if len(res) == 0:\n            return ""\n        else:\n            return str(min(res))\n\n\n        \n```
['Python3']