57 lines
1.3 KiB
C
57 lines
1.3 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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// row starts with 1; col < row
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size_t bellIndex(int row, int col) {
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return row * (row - 1) / 2 + col;
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}
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int getBell(int *bellTri, int row, int col) {
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size_t index = bellIndex(row, col);
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return bellTri[index];
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}
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void setBell(int *bellTri, int row, int col, int value) {
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size_t index = bellIndex(row, col);
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bellTri[index] = value;
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}
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int *bellTriangle(int n) {
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size_t length = n * (n + 1) / 2;
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int *tri = calloc(length, sizeof(int));
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int i, j;
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setBell(tri, 1, 0, 1);
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for (i = 2; i <= n; ++i) {
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setBell(tri, i, 0, getBell(tri, i - 1, i - 2));
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for (j = 1; j < i; ++j) {
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int value = getBell(tri, i, j - 1) + getBell(tri, i - 1, j - 1);
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setBell(tri, i, j, value);
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}
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}
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return tri;
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}
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int main() {
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const int rows = 15;
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int *bt = bellTriangle(rows);
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int i, j;
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printf("First fifteen Bell numbers:\n");
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for (i = 1; i <= rows; ++i) {
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printf("%2d: %d\n", i, getBell(bt, i, 0));
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}
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printf("\nThe first ten rows of Bell's triangle:\n");
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for (i = 1; i <= 10; ++i) {
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printf("%d", getBell(bt, i, 0));
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for (j = 1; j < i; ++j) {
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printf(", %d", getBell(bt, i, j));
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}
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printf("\n");
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}
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free(bt);
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return 0;
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}
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