Press n or j to go to the next uncovered block, b, p or k for the previous block.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 | 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 3x 59x 59x 59x 59x 59x 59x 59x 59x 59x 59x 8x 8x 59x 4x 4x 47x 47x 59x 12x 59x 35x 35x 47x 47x 47x 59x 12x 28x 28x 59x 35x 65x 65x 35x 47x 59x 233x 233x 475x 475x 233x 233x 233x 233x 52x 52x 52x 52x 52x 52x 40x 40x 64x 64x 40x 233x 181x 181x 181x 123x 123x 181x 146x 146x 58x 58x 146x 181x 233x 47x 59x 3x 3x 3x 3x 3x | /**
* @license Apache-2.0
*
* Copyright (c) 2026 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
'use strict';
// MODULES //
var binomcoef = require( '@stdlib/math/base/special/binomcoef' );
// MAIN //
/**
* Computes combinations of a specified length from double-precision floating-point strided array elements using alternative indexing semantics.
*
* @param {NonNegativeInteger} N - number of indexed elements
* @param {NonNegativeInteger} k - number of elements to combine
* @param {boolean} replacement - boolean indicating whether to allow duplication in combination
* @param {Float64Array} x - input array
* @param {integer} strideX - stride length for `x`
* @param {NonNegativeInteger} offsetX - starting index for `x`
* @param {Float64Array} out - output array
* @param {integer} strideOut1 - stride length for the first dimension of `out`
* @param {integer} strideOut2 - stride length for the second dimension of `out`
* @param {NonNegativeInteger} offsetOut - starting index for `out`
* @returns {Float64Array} output array
*
* @example
* var Float64Array = require( '@stdlib/array/float64' );
*
* var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0 ] );
* var out = new Float64Array( 12 );
*
* dcombinations( 4, 2, false, x, 1, 0, out, 2, 1, 0 );
* // out => <Float64Array>[ 1.0, 2.0, 1.0, 3.0, 1.0, 4.0, 2.0, 3.0, 2.0, 4.0, 3.0, 4.0 ]
*/
function dcombinations( N, k, replacement, x, strideX, offsetX, out, strideOut1, strideOut2, offsetOut ) { // eslint-disable-line max-len
var indices;
var val;
var io;
var C;
var c;
var i;
var j;
if ( N <= 0 || k <= 0 ) {
return out;
}
if ( !replacement && k > N ) {
return out;
}
// Compute total number of combinations:
if ( replacement ) {
C = binomcoef( N + k - 1, k );
} else {
C = binomcoef( N, k );
}
// Initialize combination index array:
indices = [];
if ( replacement ) {
for ( i = 0; i < k; i++ ) {
indices[ i ] = 0;
}
} else {
for ( i = 0; i < k; i++ ) {
indices[ i ] = i;
}
}
io = offsetOut;
for ( c = 0; c < C; c++ ) {
// Write current combination to output:
for ( j = 0; j < k; j++ ) {
out[ io + (j * strideOut2) ] = x[ offsetX + (indices[ j ] * strideX) ]; // eslint-disable-line max-len
}
io += strideOut1;
// Advance to next combination:
if ( replacement ) {
// Find rightmost index that can be incremented:
j = k - 1;
while ( j >= 0 && indices[ j ] === N - 1 ) {
j -= 1;
}
if ( j >= 0 ) {
val = indices[ j ] + 1;
for ( i = j; i < k; i++ ) {
indices[ i ] = val;
}
}
} else {
// Find rightmost index that can be incremented:
j = k - 1;
while ( j >= 0 && indices[ j ] === N - k + j ) {
j -= 1;
}
if ( j >= 0 ) {
indices[ j ] += 1;
for ( i = j + 1; i < k; i++ ) {
indices[ i ] = indices[ i - 1 ] + 1;
}
}
}
}
return out;
}
// EXPORTS //
module.exports = dcombinations;
|