_2570. Merge Two 2D Arrays by Summing Values.md

2570. Merge Two 2D Arrays by Summing Values

All prompts are owned by LeetCode. To view the prompt, click the title link above.

Back to top

---

First completed : June 10, 2024

Last updated : July 01, 2024

---

Related Topics : Array, Hash Table, Two Pointers

Acceptance Rate : 74.18 %

---

Solutions

• e2570 v1.c
• e2570 v2 less mallocing.c

C

e2570 v1.c

/**
 * Return an array of arrays of size *returnSize.
 * The sizes of the arrays are returned as *returnColumnSizes array.
 * Note: Both returned array and *columnSizes array must be malloced, assume caller calls free().
 */
int** mergeArrays(int** nums1, int nums1Size, int* nums1ColSize, int** nums2, int nums2Size, int* nums2ColSize, int* returnSize, int** returnColumnSizes){
    // To act in effect as a hashmap of size 1001 so we can just place 
    // the vals here temporarily
    int** output = (int**) malloc(sizeof(int*) * (1000 + 1));

    // Initializing and setting space
    for (int i = 0; i < 1000 + 1; i++) {
        output[i] = (int*) malloc(sizeof(int) * 2);
        output[i][0] = 0;
    }


    // Going through each of the input vals
    int numValsInOutput = 0;

    for (int i = 0; i < nums1Size; i++) {
        if (output[nums1[i][0]][0] == 0) {
            output[nums1[i][0]][0] = nums1[i][0];
            output[nums1[i][0]][1] = nums1[i][1];
            numValsInOutput++;
        } else {
            output[nums1[i][0]][1] += nums1[i][1];
        }
    }

    for (int i = 0; i < nums2Size; i++) {
        if (output[nums2[i][0]][0] == 0) {
            output[nums2[i][0]][0] = nums2[i][0];
            output[nums2[i][0]][1] = nums2[i][1];
            numValsInOutput++;
        } else {
            output[nums2[i][0]][1] += nums2[i][1];
        }
    }

    // Mallocing and filling the actual output space
    int** realOutput = (int**) malloc(sizeof(int*) * numValsInOutput);
    *returnSize = numValsInOutput;
    *returnColumnSizes = (int*) malloc(sizeof(int) * numValsInOutput);

    int pos = 0;
    int outputPos = 0;
    while (pos < numValsInOutput) {
        if (output[outputPos][0] != 0) {
            realOutput[pos] = (int*) malloc(sizeof(int) * 2);
            realOutput[pos][0] = output[outputPos][0];
            realOutput[pos][1] = output[outputPos][1];
            (*returnColumnSizes)[pos] = 2;
            pos++;
        }
        outputPos++;
    }


    // Freeing our previous values
    for (int i = 0; i < nums1Size + nums2Size; i++) {
        free(output[i]);    
    }
    free(output);

    return realOutput;
}

e2570 v2 less mallocing.c

/**
 * Return an array of arrays of size *returnSize.
 * The sizes of the arrays are returned as *returnColumnSizes array.
 * Note: Both returned array and *columnSizes array must be malloced, assume caller calls free().
 */
int** mergeArrays(int** nums1, int nums1Size, int* nums1ColSize, int** nums2, int nums2Size, int* nums2ColSize, int* returnSize, int** returnColumnSizes){
    // To act in effect as a hashmap of size 1001 so we can just place 
    // the vals here temporarily
    int output[2 * 1001] = {0};

    // Going through each of the input vals
    int numValsInOutput = 0;

    for (int i = 0; i < nums1Size; i++) {
        if (output[nums1[i][0] * 2] == 0) {
            output[nums1[i][0] * 2] = nums1[i][0];
            output[nums1[i][0] * 2 + 1] = nums1[i][1];
            numValsInOutput++;
        } else {
            output[nums1[i][0] * 2 + 1] += nums1[i][1];
        }
    }

    for (int i = 0; i < nums2Size; i++) {
        if (output[nums2[i][0] * 2] == 0) {
            output[nums2[i][0] * 2] = nums2[i][0];
            output[nums2[i][0] * 2 + 1] = nums2[i][1];
            numValsInOutput++;
        } else {
            output[nums2[i][0] * 2 + 1] += nums2[i][1];
        }
    }

    // Mallocing and filling the actual output space
    int** realOutput = (int**) malloc(sizeof(int*) * numValsInOutput);
    *returnSize = numValsInOutput;
    *returnColumnSizes = (int*) malloc(sizeof(int) * numValsInOutput);

    int pos = 0;
    int outputPos = 0;
    while (pos < numValsInOutput) {
        if (output[outputPos] != 0) {
            realOutput[pos] = (int*) malloc(sizeof(int) * 2);
            realOutput[pos][0] = output[outputPos];
            realOutput[pos][1] = output[outputPos + 1];
            (*returnColumnSizes)[pos] = 2;
            pos++;
        }
        outputPos += 2;
    }

    return realOutput;
}