标签：判断 元素 ems syn ref htm turn lsp http
一、康托展开：全排列到一个自然数的双射
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#include<cstdio> const int fac[] = {1, 1, 2, 6, 24, 120, 720, 5040, 40320};///阶乘 int KT(int s[], int n) { int i, j, cnt, sum; sum = 0; for (i = 0; i < n; ++i) { cnt = 0; for (j = i + 1; j < n; ++j) if (s[j] < s[i]) ++cnt; sum += cnt * fac[n - i - 1]; } return sum; } int main() { int a[] = {3, 5, 7, 4, 1, 2, 9, 6, 8}; printf("%d\n", 1 + KT(a, sizeof(a) / sizeof(*a))); ///1+98884 } |
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#include<cstdio> #include<cstring> const int fac[] = {1, 1, 2, 6, 24, 120, 720, 5040, 40320};///阶乘 bool vis[10]; ///n为ans大小，k为全排列的编码 void invKT(int ans[], int n, int k) { int i, j, t; memset(vis, 0, sizeof(vis)); --k; for (i = 0; i < n; ++i) { t = k / fac[n - i - 1]; for (j = 1; j <= n; j++) if (!vis[j]) { if (t == 0) break; --t; } ans[i] = j, vis[j] = true; k %= fac[n - i - 1];///余数 } } int main() { int a[10]; invKT(a, 5, 16); for (int i = 0; i < 5; ++i) printf("%d ", a[i]);///1 4 3 5 2 } |
标签：判断 元素 ems syn ref htm turn lsp http
原文地址：http://www.cnblogs.com/yzm10/p/7183439.html
