76 lines
1.6 KiB
C
76 lines
1.6 KiB
C
/* mbinary
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#########################################################################
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# File : permute_cantor.c
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# Author: mbinary
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# Mail: zhuheqin1@gmail.com
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# Blog: https://mbinary.xyz
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# Github: https://github.com/mbinary
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# Created Time: 2018-11-17 11:25
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# Description:
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#########################################################################
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*/
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#include<stdio.h>
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//使用康托展开计算全排列, 下面存储的是0!,1!,2!...(n-1)!
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long long int fac[100] = {};
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void calFac(int n)
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{
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int i;
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fac[0] = 1;
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for (i = 1; i <= n; i++) {
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fac[i] = i * fac[i - 1];
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}
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}
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void permute(int *arr, int n, int sum)
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{
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/*sum表示全排列由小到大排序后的名次,从0 开始计数, 由名次求出 n位的排列存储到 arr 中*/
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int i, j, ct = 0, k, ct2;
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int flag[n];
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for (i = 0; i < n; i++)flag[i] = 1;
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for (i = n - 1; i >= 0; i--) {
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for (j = i; j >= 0; j--) {
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if (j * fac[i] <= sum) {
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ct2 = 0;
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for (k = 0; k < n; ++k) {
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//printf("i%d j%d k%d\n",i,j,k);
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if (flag[k] == 1)ct2++;
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if (ct2 > j)break;
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}
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arr[ct++] = k;
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flag[k] = 0;
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sum -= j * fac[i];
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break;
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}
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}
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}
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}
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void printArr(int *p, int n)
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{
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for (int i = 0; i < n; ++i)printf("%d, ", p[i]);
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printf("\n");
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}
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int main()
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{
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int n = 5, arr[n];
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calFac(n);
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for (int i = 0; i < 5; ++i)arr[i] = i;
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for (int i = 0; i < fac[n]; ++i) {
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printArr(arr, n);
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permute(arr, n, i);
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}
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return 0;
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}
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