画解算法 38-报数 about blog HOT 3 CLOSED

guanpengchn commented on June 15, 2024

画解算法 38-报数

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Comments (3)

dljgs1 commented on June 15, 2024

可以投机取巧取得非常快的速度……

生成30内的答案
res = ["","1"]
for i in range(2,31):
num = res[i-1][0]
ct = 0
ans = ""
for s in res[i-1]:
if num == s:
ct += 1
else:
ans += str(ct)+num
num = s
ct = 1
if num is not None and ct>0:
ans += str(ct)+num
res.append(ans)
import json
print(json.dumps(res))
把答案复制到代码前，求解函数只需要一句话
ans = …………
class Solution:
def countAndSay(self, n: int) -> str:
return ans[n]

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LoneRanger66 commented on June 15, 2024

一刷的代码：

class Solution {
    public String countAndSay(int n) {
        StringBuilder s = new StringBuilder("1");
        while (--n > 0) {
            StringBuilder tmp = new StringBuilder();
            for (int i = 0; i < s.length(); i++) {
                int count = 1;
                char c = s.charAt(i);
                while (i < s.length() - 1 && s.charAt(i + 1) == c) {
                    i++;
                    count++;
                }
                tmp.append(count).append(c);
            }
            s = tmp;
        }
        return s.toString();
    }
}

二刷的代码：

class Solution {
    public String countAndSay(int n) {
        String ans = "1";
        for (int i = 2; i <= n; i++) {
            ans = generate(ans);
        }
        return ans;
    }

    private String generate(String s) {
        StringBuilder sb = new StringBuilder();
        int count = 1;
        for (int i = 1; i < s.length(); i++) {
            if (s.charAt(i) == s.charAt(i - 1)) {
                count++;
            } else {
                sb.append(count).append(s.charAt(i - 1));
                count = 1;
            }
        }
        sb.append(count).append(s.charAt(s.length() - 1));
        return sb.toString();
    }
}

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intbjw commented on June 15, 2024

由前面的结果推后面的结果

class Solution:
    def countAndSay(self, n: int) -> str:
        def next_num(tmp):
            res = ""
            i = 0
            tmp_n = len(tmp)
            while i < tmp_n:
                count = 1
                while i < tmp_n - 1 and tmp[i] == tmp[i+1]:
                    count += 1
                    i += 1
                res += (str(count) + tmp[i])
                i += 1
            return res
        res = "1"
        for i in range(1, n):
            res = next_num(res)
        return res

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