perf: 1.c faster implementation of the leetcode TwoSum problem

DIRECTORY.md

@@ -94,7 +94,9 @@
     * [List](https://github.com/TheAlgorithms/C/blob/master/data_structures/list/list.c)
     * [List](https://github.com/TheAlgorithms/C/blob/master/data_structures/list/list.h)
     * [Main](https://github.com/TheAlgorithms/C/blob/master/data_structures/list/main.c)
-  * [Queue](https://github.com/TheAlgorithms/C/blob/master/data_structures/queue.c)
+  * Queue
+    * [Include](https://github.com/TheAlgorithms/C/blob/master/data_structures/queue/include.h)
+    * [Queue](https://github.com/TheAlgorithms/C/blob/master/data_structures/queue/queue.c)
   * [Stack](https://github.com/TheAlgorithms/C/blob/master/data_structures/stack.c)
   * Stack
     * [Main](https://github.com/TheAlgorithms/C/blob/master/data_structures/stack/main.c)

leetcode/src/1.c

@@ -1,17 +1,168 @@
-int *twoSum(int *nums, int numsSize, int target, int *returnSize)
+/**
+ * @file
+ * @brief TwoSum leetcode problem solution.
+ * @details
+ * This is a recursive solution for the leetcode problem of TwoSum.
+ * @author [straight_into_the_wall](https://github.com/straight-into-the-wall)
+ * @see https://leetcode.com/problems/two-sum/
+ */
+
+#include <assert.h>  /// for assert
+#include <stdint.h>  /// for unsigned int with fixed size
+#include <stdlib.h>  /// for everithing else
+
+int* ending(int* a, int* b, int* returnSize);
+
+/**
+ * @brief Given an array of integers and an integer target,
+ * find the two numbers such that they add up to a given target.
+ * @param nums the array of integer to be processed.
+ * @param numsSize the size of array on input.
+ * @param target the integer to be matched.
+ * @param returnSize a pointer to the size of the output array.
+ * @returns an array of the indices of the two numbers such that they add up to
+ * target.
+ */
+int* twoSum(int* nums, int numsSize, int target, int* returnSize)
+{
+    int needle = target - nums[--numsSize];
+
+    for (int i = numsSize - 1; i >= 0; i--)
+        if (needle == nums[i])
+            return ending(&i, &numsSize, returnSize);
+
+    return twoSum(nums, numsSize, target, returnSize);
+}
+
+/**
+ * @brief Prepare the output at the end of the execution. Just to keep tidy the
+ * main function.
+ * @param a an index of the solution.
+ * @param b the other index of the solution.
+ * @param returnSize a pointer to the size of the output array (always 2 on
+ * success).
+ * @returns an array of the indices of the two numbers such that they add up to
+ * target.
+ */
+int* ending(int* a, int* b, int* returnSize)
 {
-    int i, j;
-    int *ret = calloc(2, sizeof(int));
-    for (i = 0; i < numsSize; i++)
-    {
-        int key = target - nums[i];
-        for (j = i + 1; j < numsSize; j++)
-            if (nums[j] == key)
-            {
-                ret[0] = i;
-                ret[1] = j;
-            }
-    }
     *returnSize = 2;
+    int* ret = calloc(*returnSize, sizeof(int));
+    ret[0] = *a;
+    ret[1] = *b;
     return ret;
 }
+
+/**
+ * @brief Self-test implementations
+ * @returns void
+ */
+static void testTwoSum(int* nums, int numsSize, int target)
+{
+    int retSize = 0;
+    int* ret = twoSum(nums, numsSize, target, &retSize);
+
+    for (int i = 0; i < retSize; i++) target -= nums[ret[i]];
+
+    free(ret);
+    assert(!target);
+}
+
+static void test(void)
+{
+    int nums[4] = {2, 7, 15, 11};
+    testTwoSum(nums, 4, 9);
+
+    int nums1[4] = {2, -7, 11, 15};
+    testTwoSum(nums1, 4, 4);
+
+    int nums2[3] = {3, 2, 4};
+    testTwoSum(nums2, 3, 6);
+
+    int nums3[2] = {3, 3};
+    testTwoSum(nums3, 2, 6);
+
+    int nums4[3] = {3, -3, 6};
+    testTwoSum(nums4, 3, 0);
+
+    int nums5[6] = {-13, 0, 13, 7, -3, 6};
+    testTwoSum(nums5, 6, -7);
+
+    int nums6[5] = {-1, -2, -3, -4, -5};
+    testTwoSum(nums6, 5, -8);
+
+    int nums7[] = {
+        1931729,  5896941,  -56160,   -5999108, -713650,  3135403,  870300,
+        -2938196, -726482,  -152831,  -5552046, -6857780, 2493109,  -2409591,
+        7453630,  7848984,  -806578,  4976647,  -9199319, -7660981, 4168359,
+        5466164,  8577624,  -7465790, -7808993, -7176396, -3622579, 4996177,
+        9623530,  -1371773, -5633028, 5188756,  7971646,  -2603602, 7490338,
+        3174208,  -1825054, 6892503,  -8201151, -1072749, -2746872, -718104,
+        -1804706, 5504856,  -9104958, -2181797, 3151933,  -6116343, 1436458,
+        -659793,  -9256591, -3487143, 3396195,  -6211129, -2789647, -9336842,
+        -122743,  -3843085, 8515885,  -8551842, -8668581, -5040156, -9626107,
+        -5645393, -5484621, -6417906, 4483313,  -4197219, -5762688, -6645419,
+        1077632,  7237401,  4819732,  5220382,  8657346,  651862,   7406097,
+        6668849,  5067699,  4563307,  -4358391, -3996666, -4298897, -9870277,
+        -628517,  1842975,  -4970541, -8815324, -4174656, -9332000, 4647373,
+        9461387,  -3504914, 2614670,  -1315721, 6099266,  -8562834, -4488116,
+        9742133,  307556,   791291,   -2611787, 7656675,  9932436,  -1905766,
+        5142745,  7210001,  -4678645, 550797,   8462302,  6815722,  -2985059,
+        -1236401, -6093644, -6617192, -9438320, 8400183,  8936598,  5378080,
+        9758788,  817106,   8613435,  3579880,  -9100698, 993960,   5352546,
+        8481471,  3526666,  2961295,  -7819498, 834324,   3435605,  9725655,
+        8490290,  7263645,  -6863345, 2947003,  -8152353, 5514173,  -9865666,
+        343864,   -6386758, -8675825, -3252881, 1149651,  6690889,  7528843,
+        -2861961, -4722247, -6985318, -9994086, 7192089,  -4864512, 5773490,
+        -9492163, -2089496, 2246943,  430576,   3466065,  1578813,  2738295,
+        261493,   -425120,  3666399,  8796329,  9220040,  7148637,  5956722,
+        9980401,  7834421,  2041136,  3763240,  -831391,  7963736,  8744496,
+        9593751,  4606042,  66708,    -6652782, -6619264, 2614784,  5655774,
+        -9547771, 2456855,  4268450,  864132,   4601358,  -3464052, -8987625,
+        -4427713, -126397,  -5823810, 8443040,  -7428684, -4365060, -6392451,
+        -6258724, -9124302, -6566562, -4153846, -9120859, 7061892,  -7707777,
+        9342864,  -2133124, -7068189, -8657201, 2752682,  -9943634, -8650517,
+        -5219095, 2305245,  -1500154, 8915790,  -2805210, 1860598,  3361037,
+        -8040669, 5809813,  -2243400, -3418428, -1810675, -5203397, -7879177,
+        6898143,  7749161,  -2810814, -7525359, -793458,  608571,   -9383497,
+        9531109,  6862130,  -3381989, 2332039,  6018975,  -3350279, 7266303,
+        -7170480, -1127784, 578313,   6018329,  8822950,  4214273,  -372530,
+        2706552,  -4905224, 3324641,  -5403812, 9319424,  -2882974, -9228107,
+        6151855,  2634284,  7000575,  3215247,  5067619,  5076150,  1595871,
+        748735,   -9225927, 1962290,  4653714,  697462,   2996679,  -7562085,
+        -5387705, -912530,  1763635,  -6139098, 2103001,  -6316004, -3469182,
+        -3818553, 8854173,  422707,   -3826706, -9777012, 7452324,  3665456,
+        -9458220, 4828502,  2641583,  5107388,  -4201437, 5486625,  -9315573,
+        1417427,  -1838955, 9042987,  -9704280, 7868946,  -6737802, 4462332,
+        -5771637, 635858,   1438260,  8940144,  9385885,  3522022,  -9736738,
+        -4387243, -8611088, 8733735,  -2087884, 8299364,  -1004025, 2674570,
+        4247204,  1972151,  -2092476, -1318052, -796315,  -6487458, 8714867,
+        -9966767, -5459861, -1286737, 9442201,  -2065902, 2575270,  7184243,
+        5916475,  -5728128, -3044939, 6372732,  4902791,  3474374,  -7462481,
+        -9886552, -8361835, -5022392, -4583670, 3990789,  -1051830, 8606314,
+        6365011,  6751820,  1727390,  -2005234, -5845824, 9572998,  6867269,
+        4000416,  5629823,  -2918551, 7278467,  9865305,  3781390,  -1518411,
+        -7124219, 3800842,  -4492377, -7479001, 4144917,  4639464,  7161451,
+        3391326,  -2429792, 8240315,  -8667371, 101661,   -6049927, -9729041,
+        -2210443, -6907416, -1355534, 6292201,  -1169114, -4565077, 3214740,
+        -6122903, 8326559,  -3973709, 2313703,  9645383,  6119383,  8317176,
+        8177731,  7758979,  3037198,  -9543017, -3436171, 3280360,  -1444577,
+        -40402,   -8372623, 6672469,  9125222,  6161730,  3783090,  -2778572,
+        -8014616, -1588372, -3200391, 7126312,  -5091311, -3637052, -6600914,
+        9034974,  -6246289, -4974981, -9711741, -7867786, -9808240, 450272,
+        -3222991, -8251454, 3599528,  -33487,   -1114626, 8414308,  -2607016,
+        1690025,  5981016,  -2898849, -4650973, -8085619, -4875585, -2677275,
+        -7329644, -9730701, -5563788, 4635028,  -4232606, 1863619,  -9081061,
+        -8966306, 4907349,  348942,   -6309867, 2436213,  -6340842, 8276407,
+        -1112458, 4073087,  6632641,  -6044509, -1714553, -9905887, 8140713,
+        -5566484, -8187046, -3636448, 560425,   9931445,  -8142363, 1928694,
+        6652925,  5094575,  5525595,  9847315,  5323311,  9123454,  7425631,
+        2116547,  9033708,  -2228326, 2858537,  5452249,  -3388576, 8859366,
+        5965629,  -9904937, 8961420,  -8794807, 4363288,  -1067547, 1903643,
+        -6637956, 3736544,  9150157,  -3977433, 4333094,  -1170635, -4933425,
+        5815702,  1846616,  793301,   -9206787, -227043,  -7076926, -461803,
+        -7477454, -1297664, 47425,    8506054,  8264895,  -1199514, -4031592,
+        1245359,  2840097,  6948011};
+
+    testTwoSum(nums7, 492, 7828670);
+}