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+// 885. Spiral Matrix III
+#include "leetcode.h"
+
+/*
+ * you start at the cell '(rStart, cStart)' of an 'rows * cols' grid facing
+ * east. the northwest corner is at the first row and column in the grid, and
+ * the southeast corner is at the last row and column. you will walk in a
+ * clockwise spiral shape to visit every position in this gid. whenever you move
+ * outside the grid's boundary, we continue our walk outside the grid (but may
+ * return to the gid boundary later). eventually we reach all 'rows * cols'
+ * spaces of the grid. return an array of coordinates representing the positions
+ * of the grid in the order visited.
+ */
+
+int **spiralMatrixIII(int rows, int cols, int rStart, int cStart,
+ int *returnSize, int **returnColumnSizes) {
+ *returnSize = rows * cols;
+ *returnColumnSizes = (int *)malloc((*returnSize) * sizeof(int));
+ int **ans = (int **)malloc((*returnSize) * sizeof(int *));
+ for (int i = 0; i < (*returnSize); i++) {
+ ans[i] = (int *)calloc(2, sizeof(int));
+ (*returnColumnSizes)[i] = 2;
+ }
+ ans[0][0] = rStart;
+ ans[0][1] = cStart;
+ int up = 1, right = 1, cnt_rl = 0, cnt_ud = 0, idx = 1;
+ while (idx < (*returnSize)) {
+ for (int shift = 1; shift <= right; shift++) {
+ cStart = !(cnt_rl % 2) ? cStart + 1 : cStart - 1;
+ if (rStart < rows && cStart < cols && rStart > -1 && cStart > -1) {
+ ans[idx][0] = rStart;
+ ans[idx][1] = cStart;
+ idx++;
+ }
+ }
+ cnt_rl++, right++;
+ for (int shift = 1; shift <= up; shift++) {
+ rStart = !(cnt_ud % 2) ? rStart + 1 : rStart - 1;
+ if (rStart < rows && cStart < cols && rStart > -1 && cStart > -1) {
+ ans[idx][0] = rStart;
+ ans[idx][1] = cStart;
+ }
+ }
+ cnt_ud++, up++;
+ }
+ return ans;
+}
+
+int main() {
+ int rs1, rs2, **rcs1, **rcs2;
+ int **sm31 = spiralMatrixIII(1, 4, 0, 0, &rs1, rcs1);
+ int **sm32 = spiralMatrixIII(5, 6, 1, 4, &rs1, rcs2);
+ for (int i = 0; i < rs1; i++)
+ for (int j = 0; j < rcs1[i][j]; j++)
+ printf("%d ", sm31[i][j]);
+ printf("\n");
+ for (int i = 0; i < rs2; i++)
+ for (int j = 0; j < rcs2[i][j]; j++)
+ printf("%d ", sm32[i][j]);
+ printf("\n");
+ for (int i = 0; i < rs1; i++)
+ free(sm31[i]);
+ for (int i = 0; i < rs2; i++)
+ free(sm32[i]);
+ free(sm31), free(sm32);
+}