C 尝试比较两种排序算法的空间复杂度。Don'；我不知道如何解释这个答案

我有两种排序算法，合并排序和插入排序。我试图检查它们在执行期间分配了多少ram内存，以便进行比较。两者都在对1000个元素的数组进行排序，整数在0-999之间

这些程序被编译成名为

main

（

merge\u sort/main

和

insertion\u sort/main

）的二进制文件。所以我在跑步：

memusage -T ./main

在这两种算法上

两个返回：

heap total: 73728, heap peak: 73728, stack peak: 6144

为什么它们返回相同的值？合并排序不应该比插入排序分配更多内存吗？我是否使用了

memusage

正确

我还尝试使用Valgrind对它们进行检查，Valgrind也会返回相同的结果：

==26544== HEAP SUMMARY:
==26544==     in use at exit: 0 bytes in 0 blocks
==26544==   total heap usage: 2 allocs, 2 frees, 73,728 bytes allocated

我的理论是：要么我不知道自己在做什么

或者排序的列表太小。因此，内存使用情况看起来是相同的

代码：

合并排序

/* C program for Merge Sort */
#include<stdlib.h>
#include<stdio.h>
#include<time.h>

// Merges two subarrays of arr[].
// First subarray is arr[l..m]
// Second subarray is arr[m+1..r]
void merge(int arr[], int l, int m, int r)
{
    int i, j, k;
    int n1 = m - l + 1;
    int n2 = r - m;

    /* create temp arrays */
    int L[n1], R[n2];

    /* Copy data to temp arrays L[] and R[] */
    for (i = 0; i < n1; i++)
        L[i] = arr[l + i];
    for (j = 0; j < n2; j++)
        R[j] = arr[m + 1+ j];

    /* Merge the temp arrays back into arr[l..r]*/
    i = 0; // Initial index of first subarray
    j = 0; // Initial index of second subarray
    k = l; // Initial index of merged subarray
    while (i < n1 && j < n2)
    {
        if (L[i] <= R[j])
        {
            arr[k] = L[i];
            i++;
        }
        else
        {
            arr[k] = R[j];
            j++;
        }
        k++;
    }

    /* Copy the remaining elements of L[], if there
    are any */
    while (i < n1)
    {
        arr[k] = L[i];
        i++;
        k++;
    }

    /* Copy the remaining elements of R[], if there
    are any */
    while (j < n2)
    {
        arr[k] = R[j];
        j++;
        k++;
    }
}

/* l is for left index and r is right index of the
sub-array of arr to be sorted */
void mergeSort(int arr[], int l, int r)
{
    if (l < r)
    {
        // Same as (l+r)/2, but avoids overflow for
        // large l and h
        int m = l+(r-l)/2;

        // Sort first and second halves
        mergeSort(arr, l, m);
        mergeSort(arr, m+1, r);

        merge(arr, l, m, r);
    }
}

/* UTILITY FUNCTIONS */
/* Function to print an array */
void printArray(int A[], int size)
{
    int i;
    for (i=0; i < size; i++)
        printf("%d ", A[i]);
    printf("\n");
}

/* Driver program to test above functions */
int main()
{
    int arr[] = {
        397, 326, 157, 581, 198, 158, 107, 479, 919, 288, 118, 14, 384, 389, 354, 905, 648, 24, 639, 279, 846, 896, 901, 491, 827, 502, 119, 520, 544, 688, 433, 542, 280, 834, 574, 739, 168, 714, 367, 547, 555, 616, 71, 583, 77, 372, 380, 414, 80, 828, 671, 900, 710, 852, 810, 471, 493, 832, 310, 579, 605, 174, 19, 576, 162, 695, 635, 851, 265, 48, 536, 228, 754, 300, 610, 272, 619, 825, 770, 147, 9, 813, 525, 135, 768, 654, 889, 446, 910, 678, 432, 172, 618, 41, 839, 589, 304, 484, 765, 357, 427, 617, 75, 683, 930, 593, 341, 149, 733, 27, 556, 474, 987, 156, 501, 665, 370, 523, 142, 420, 114, 798, 989, 382, 543, 879, 294, 305, 684, 331, 443, 383, 625, 647, 780, 811, 34, 621, 744, 842, 150, 938, 301, 495, 965, 392, 634, 358, 570, 789, 266, 242, 709, 278, 932, 57, 952, 475, 984, 136, 133, 637, 734, 207, 697, 362, 344, 332, 89, 529, 188, 164, 124, 317, 103, 257, 514, 364, 356, 203, 112, 831, 867, 644, 815, 452, 456, 260, 291, 90, 13, 21, 160, 217, 251, 459, 213, 110, 455, 56, 753, 127, 349, 884, 434, 982, 224, 410, 104, 540, 640, 973, 486, 945, 201, 166, 99, 535, 229, 725, 361, 483, 190, 743, 998, 409, 159, 102, 55, 219, 720, 33, 971, 859, 335, 887, 538, 363, 557, 696, 11, 951, 51, 845, 231, 723, 569, 63, 903, 185, 406, 505, 833, 309, 49, 599, 788, 511, 990, 196, 324, 803, 247, 970, 440, 504, 627, 205, 656, 308, 948, 690, 551, 819, 988, 608, 67, 519, 907, 510, 603, 256, 597, 880, 893, 214, 95, 270, 915, 179, 298, 378, 550, 953, 717, 321, 992, 863, 796, 868, 604, 152, 368, 15, 284, 17, 925, 808, 799, 841, 946, 974, 450, 546, 682, 91, 666, 402, 283, 736, 567, 679, 125, 299, 319, 762, 849, 785, 264, 797, 623, 401, 689, 140, 461, 171, 454, 624, 853, 724, 191, 130, 86, 451, 87, 109, 38, 61, 413, 348, 289, 829, 969, 670, 528, 588, 937, 766, 885, 237, 823, 592, 184, 73, 239, 643, 180, 10, 195, 277, 787, 431, 562, 390, 338, 146, 638, 85, 424, 652, 2, 631, 685, 405, 35, 387, 912, 333, 740, 692, 769, 66, 554, 565, 926, 223, 322, 826, 657, 858, 703, 1, 986, 312, 246, 31, 577, 323, 145, 439, 375, 39, 170, 106, 478, 978, 716, 254, 756, 37, 360, 350, 463, 269, 52, 64, 386, 509, 997, 429, 379, 655, 916, 878, 553, 794, 807, 197, 16, 840, 947, 860, 920, 963, 70, 183, 572, 763, 192, 729, 340, 238, 209, 469, 151, 167, 292, 303, 129, 847, 749, 4, 218, 216, 924, 215, 784, 243, 394, 836, 782, 476, 268, 78, 54, 590, 81, 908, 23, 704, 428, 778, 976, 680, 211, 622, 131, 273, 236, 487, 416, 767, 854, 870, 255, 837, 336, 611, 958, 233, 991, 3, 764, 83, 7, 541, 244, 792, 790, 0, 407, 418, 812, 334, 32, 872, 883, 537, 518, 72, 293, 886, 220, 866, 42, 730, 929, 891, 126, 470, 686, 329, 28, 568, 563, 659, 186, 706, 923, 497, 942, 844, 850, 492, 783, 715, 415, 153, 120, 448, 496, 468, 398, 620, 369, 373, 629, 79, 835, 711, 750, 311, 738, 346, 881, 121, 911, 50, 612, 498, 395, 955, 490, 774, 944, 506, 584, 664, 445, 173, 524, 561, 252, 713, 359, 771, 595, 96, 458, 956, 967, 422, 507, 177, 515, 342, 488, 759, 274, 275, 385, 816, 983, 306, 263, 830, 897, 760, 82, 426, 5, 698, 200, 981, 276, 559, 613, 154, 532, 735, 84, 345, 909, 94, 202, 302, 580, 508, 44, 134, 374, 898, 100, 993, 116, 712, 943, 646, 552, 975, 800, 6, 824, 328, 318, 960, 245, 708, 548, 403, 60, 931, 499, 676, 88, 894, 465, 921, 817, 693, 591, 957, 818, 721, 596, 649, 935, 261, 747, 391, 917, 314, 296, 460, 376, 412, 227, 240, 139, 871, 776, 691, 513, 93, 606, 531, 464, 694, 977, 108, 69, 259, 466, 417, 58, 737, 786, 43, 707, 933, 307, 74, 719, 653, 327, 746, 913, 262, 922, 731, 199, 494, 804, 877, 873, 732, 285, 727, 47, 210, 927, 914, 194, 758, 602, 582, 566, 941, 598, 809, 672, 966, 258, 137, 961, 902, 467, 92, 105, 316, 29, 234, 781, 675, 286, 226, 353, 857, 777, 472, 68, 985, 480, 330, 250, 248, 282, 962, 838, 176, 208, 40, 175, 178, 281, 396, 444, 436, 560, 521, 895, 366, 377, 586, 578, 212, 641, 232, 687, 571, 876, 585, 117, 101, 862, 701, 934, 939, 968, 189, 53, 677, 573, 869, 113, 642, 65, 607, 143, 979, 645, 856, 352, 20, 522, 249, 355, 148, 22, 473, 742, 98, 347, 419, 477, 705, 674, 757, 899, 430, 489, 425, 949, 726, 950, 123, 667, 399, 297, 594, 650, 587, 503, 141, 442, 748, 221, 775, 500, 339, 668, 400, 45, 814, 516, 663, 996, 772, 882, 230, 267, 722, 404, 821, 204, 755, 12, 702, 435, 822, 315, 630, 673, 848, 438, 482, 408, 928, 512, 371, 779, 626, 235, 527, 462, 904, 651, 661, 411, 752, 36, 980, 761, 485, 855, 241, 222, 287, 46, 802, 801, 206, 453, 111, 874, 295, 59, 628, 806, 290, 575, 600, 337, 728, 995, 138, 609, 875, 193, 30, 658, 558, 76, 481, 890, 745, 615, 132, 614, 795, 393, 351, 741, 564, 805, 457, 313, 545, 632, 964, 381, 25, 533, 26, 633, 62, 530, 751, 517, 936, 791, 820, 155, 940, 365, 843, 8, 918, 662, 225, 681, 388, 187, 660, 144, 793, 773, 181, 421, 161, 423, 447, 169, 994, 669, 700, 163, 526, 999, 959, 437, 449, 888, 271, 954, 18, 253, 320, 892, 864, 718, 865, 601, 699, 972, 549, 115, 441, 128, 861, 539, 165, 534, 325, 636, 122, 97, 182, 906, 343
    };
    int n = sizeof(arr)/sizeof(arr[0]);

    clock_t begin = clock();

    /* here, do your time-consuming job */
    mergeSort(arr, 0, n-1);

    clock_t end = clock();
    double time_spent = (double)(end - begin) / CLOCKS_PER_SEC;

    printf("Merge: %.10f", time_spent);
    printf("\n");
    return 0;
}

用于合并排序的C程序*/ #包括 #包括 #包括 //合并arr[]的两个子阵列。 //第一个子阵是arr[l..m] //第二个子阵是arr[m+1..r] 无效合并（整数arr[]，整数l，整数m，整数r） { int i，j，k； int n1=m-l+1； int n2=r-m； /*创建临时阵列*/ int L[n1]，R[n2]； /*将数据复制到临时数组L[]和R[]*/ 对于（i=0；i键）{ arr[j+1]=arr[j]； j=j-1； } arr[j+1]=键； } } //打印大小为n的数组的实用函数 无效打印数组（int arr[]，int n） { int i； 对于（i=0；i// C program for insertion sort #include <math.h> #include <stdio.h> #include <time.h> #include <unistd.h> /* Function to sort an array using insertion sort*/ void insertionSort(int arr[], int n) { int i, key, j; for (i = 1; i < n; i++) { key = arr[i]; j = i - 1; /* Move elements of arr[0..i-1], that are greater than key, to one position ahead of their current position */ while (j >= 0 && arr[j] > key) { arr[j + 1] = arr[j]; j = j - 1; } arr[j + 1] = key; } } // A utility function to print an array of size n void printArray(int arr[], int n) { int i; for (i = 0; i < n; i++) printf("%d ", arr[i]); printf("\n"); } /* Driver program to test insertion sort */ int main() { int arr[] = { 397, 326, 157, 581, 198, 158, 107, 479, 919, 288, 118, 14, 384, 389, 354, 905, 648, 24, 639, 279, 846, 896, 901, 491, 827, 502, 119, 520, 544, 688, 433, 542, 280, 834, 574, 739, 168, 714, 367, 547, 555, 616, 71, 583, 77, 372, 380, 414, 80, 828, 671, 900, 710, 852, 810, 471, 493, 832, 310, 579, 605, 174, 19, 576, 162, 695, 635, 851, 265, 48, 536, 228, 754, 300, 610, 272, 619, 825, 770, 147, 9, 813, 525, 135, 768, 654, 889, 446, 910, 678, 432, 172, 618, 41, 839, 589, 304, 484, 765, 357, 427, 617, 75, 683, 930, 593, 341, 149, 733, 27, 556, 474, 987, 156, 501, 665, 370, 523, 142, 420, 114, 798, 989, 382, 543, 879, 294, 305, 684, 331, 443, 383, 625, 647, 780, 811, 34, 621, 744, 842, 150, 938, 301, 495, 965, 392, 634, 358, 570, 789, 266, 242, 709, 278, 932, 57, 952, 475, 984, 136, 133, 637, 734, 207, 697, 362, 344, 332, 89, 529, 188, 164, 124, 317, 103, 257, 514, 364, 356, 203, 112, 831, 867, 644, 815, 452, 456, 260, 291, 90, 13, 21, 160, 217, 251, 459, 213, 110, 455, 56, 753, 127, 349, 884, 434, 982, 224, 410, 104, 540, 640, 973, 486, 945, 201, 166, 99, 535, 229, 725, 361, 483, 190, 743, 998, 409, 159, 102, 55, 219, 720, 33, 971, 859, 335, 887, 538, 363, 557, 696, 11, 951, 51, 845, 231, 723, 569, 63, 903, 185, 406, 505, 833, 309, 49, 599, 788, 511, 990, 196, 324, 803, 247, 970, 440, 504, 627, 205, 656, 308, 948, 690, 551, 819, 988, 608, 67, 519, 907, 510, 603, 256, 597, 880, 893, 214, 95, 270, 915, 179, 298, 378, 550, 953, 717, 321, 992, 863, 796, 868, 604, 152, 368, 15, 284, 17, 925, 808, 799, 841, 946, 974, 450, 546, 682, 91, 666, 402, 283, 736, 567, 679, 125, 299, 319, 762, 849, 785, 264, 797, 623, 401, 689, 140, 461, 171, 454, 624, 853, 724, 191, 130, 86, 451, 87, 109, 38, 61, 413, 348, 289, 829, 969, 670, 528, 588, 937, 766, 885, 237, 823, 592, 184, 73, 239, 643, 180, 10, 195, 277, 787, 431, 562, 390, 338, 146, 638, 85, 424, 652, 2, 631, 685, 405, 35, 387, 912, 333, 740, 692, 769, 66, 554, 565, 926, 223, 322, 826, 657, 858, 703, 1, 986, 312, 246, 31, 577, 323, 145, 439, 375, 39, 170, 106, 478, 978, 716, 254, 756, 37, 360, 350, 463, 269, 52, 64, 386, 509, 997, 429, 379, 655, 916, 878, 553, 794, 807, 197, 16, 840, 947, 860, 920, 963, 70, 183, 572, 763, 192, 729, 340, 238, 209, 469, 151, 167, 292, 303, 129, 847, 749, 4, 218, 216, 924, 215, 784, 243, 394, 836, 782, 476, 268, 78, 54, 590, 81, 908, 23, 704, 428, 778, 976, 680, 211, 622, 131, 273, 236, 487, 416, 767, 854, 870, 255, 837, 336, 611, 958, 233, 991, 3, 764, 83, 7, 541, 244, 792, 790, 0, 407, 418, 812, 334, 32, 872, 883, 537, 518, 72, 293, 886, 220, 866, 42, 730, 929, 891, 126, 470, 686, 329, 28, 568, 563, 659, 186, 706, 923, 497, 942, 844, 850, 492, 783, 715, 415, 153, 120, 448, 496, 468, 398, 620, 369, 373, 629, 79, 835, 711, 750, 311, 738, 346, 881, 121, 911, 50, 612, 498, 395, 955, 490, 774, 944, 506, 584, 664, 445, 173, 524, 561, 252, 713, 359, 771, 595, 96, 458, 956, 967, 422, 507, 177, 515, 342, 488, 759, 274, 275, 385, 816, 983, 306, 263, 830, 897, 760, 82, 426, 5, 698, 200, 981, 276, 559, 613, 154, 532, 735, 84, 345, 909, 94, 202, 302, 580, 508, 44, 134, 374, 898, 100, 993, 116, 712, 943, 646, 552, 975, 800, 6, 824, 328, 318, 960, 245, 708, 548, 403, 60, 931, 499, 676, 88, 894, 465, 921, 817, 693, 591, 957, 818, 721, 596, 649, 935, 261, 747, 391, 917, 314, 296, 460, 376, 412, 227, 240, 139, 871, 776, 691, 513, 93, 606, 531, 464, 694, 977, 108, 69, 259, 466, 417, 58, 737, 786, 43, 707, 933, 307, 74, 719, 653, 327, 746, 913, 262, 922, 731, 199, 494, 804, 877, 873, 732, 285, 727, 47, 210, 927, 914, 194, 758, 602, 582, 566, 941, 598, 809, 672, 966, 258, 137, 961, 902, 467, 92, 105, 316, 29, 234, 781, 675, 286, 226, 353, 857, 777, 472, 68, 985, 480, 330, 250, 248, 282, 962, 838, 176, 208, 40, 175, 178, 281, 396, 444, 436, 560, 521, 895, 366, 377, 586, 578, 212, 641, 232, 687, 571, 876, 585, 117, 101, 862, 701, 934, 939, 968, 189, 53, 677, 573, 869, 113, 642, 65, 607, 143, 979, 645, 856, 352, 20, 522, 249, 355, 148, 22, 473, 742, 98, 347, 419, 477, 705, 674, 757, 899, 430, 489, 425, 949, 726, 950, 123, 667, 399, 297, 594, 650, 587, 503, 141, 442, 748, 221, 775, 500, 339, 668, 400, 45, 814, 516, 663, 996, 772, 882, 230, 267, 722, 404, 821, 204, 755, 12, 702, 435, 822, 315, 630, 673, 848, 438, 482, 408, 928, 512, 371, 779, 626, 235, 527, 462, 904, 651, 661, 411, 752, 36, 980, 761, 485, 855, 241, 222, 287, 46, 802, 801, 206, 453, 111, 874, 295, 59, 628, 806, 290, 575, 600, 337, 728, 995, 138, 609, 875, 193, 30, 658, 558, 76, 481, 890, 745, 615, 132, 614, 795, 393, 351, 741, 564, 805, 457, 313, 545, 632, 964, 381, 25, 533, 26, 633, 62, 530, 751, 517, 936, 791, 820, 155, 940, 365, 843, 8, 918, 662, 225, 681, 388, 187, 660, 144, 793, 773, 181, 421, 161, 423, 447, 169, 994, 669, 700, 163, 526, 999, 959, 437, 449, 888, 271, 954, 18, 253, 320, 892, 864, 718, 865, 601, 699, 972, 549, 115, 441, 128, 861, 539, 165, 534, 325, 636, 122, 97, 182, 906, 343, }; int n = sizeof(arr)/sizeof(arr[0]); //printf("n: %d", n); //printf("Unsorted array: "); //printArray(arr, n); //printf("\n"); clock_t begin = clock(); /* here, do your time-consuming job */ insertionSort(arr, n); clock_t end = clock(); double time_spent = (double)(end - begin) / CLOCKS_PER_SEC; //printf("Sorted array: "); //printArray(arr, n); //printf("\n"); printf("Inser: %.10f", time_spent); printf("\n"); return 0; }

free(malloc(0));

void usage_instrumentation(void) {
    free(malloc(0));
}