week15- NO.402. Remove K Digits

最新推荐文章于 2022-10-11 15:59:56 发布

jingyu1621

最新推荐文章于 2022-10-11 15:59:56 发布

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本文链接：https://blog.youkuaiyun.com/jingyu1621/article/details/73441205

介绍一种利用贪心算法解决LeetCode移除K位数以获得最小可能整数的问题，通过具体示例说明算法实现过程。

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题目

Total Accepted: 18524
Total Submissions: 70922
Difficulty: Medium
Contributor: LeetCode

Given a non-negative integer num represented as a string, remove k digits from the number so that the new number is the smallest possible.

Note:

The length of num is less than 10002 and will be ≥ k.
The given num does not contain any leading zero.

Example 1:

Input: num = "1432219", k = 3
Output: "1219"
Explanation: Remove the three digits 4, 3, and 2 to form the new number 1219 which is the smallest.

Example 2:

Input: num = "10200", k = 1
Output: "200"
Explanation: Remove the leading 1 and the number is 200. Note that the output must not contain leading zeroes.

Example 3:

Input: num = "10", k = 2
Output: "0"
Explanation: Remove all the digits from the number and it is left with nothing which is 0.

https://leetcode.com/problems/remove-k-digits/#/description

思路

题目给定一个整数串，希望拿掉k个数字后，得到的整数串值最小。

使用贪心算法，去掉从左到右，第一次比它后面的数字大的数字。

源程序

class Solution {
public:
  string removeKdigits(string num, int k) {
        int i,n = num.size();
        if(k >= n) {
            return "0";
        }
        while(k) {
            bool f = false;
            for (i = 0; i < num.size() - 1; i++) {
                if(num[i] > num[i + 1]) {
                    f = true;
                    num = num.erase(i, 1);
                    break;
                }
            }
            if(!f) {
                num = num.substr(0, num.size() - 1);
            }
            k--;
        }
        while(num.size() > 1 && num[0] == '0') num = num.substr(1);
        return num;
    }
};