[leetcode-60-Permutation Sequence]
The set [1,2,3,…,n] contains a total of n! unique permutations.
By listing and labeling all of the permutations in order,
We get the following sequence (ie, for n = 3):
"123"
"132"
"213"
"231"
"312"
"321"
Given n and k, return the kth permutation sequence.
思路:
没有呢还。。。
string getPermutation(int n, int k) { vector<int>factorial(n + 1, 1);//保留阶乘 for (int i = 1; i <= n;i++) factorial[i] = i * factorial[i - 1]; vector<char> digits = { '1', '2', '3', '4', '5', '6', '7', '8', '9' }; string result; int num = n - 1; while (num) { int t = (k-1) / factorial[num]; //是k/(n-1)! 计算第一位数字 k = k - t * factorial[num]; result.push_back(digits[t]); digits.erase(digits.begin() + t); num--; } result.push_back(digits[k - 1]); return result; }
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