Add C solution for 417-Pacific-Atlantic-Water-Flow

c/417-Pacific-Atlantic-Water-Flow.c

@@ -0,0 +1,83 @@
+
+
+/**
+ * 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 directions[4][2] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
+bool pacific_reach[200][200];
+bool atlantic_reach[200][200];
+
+void resetSet(bool set[200][200]) {
+ for (int i = 0; i < 200; i++) {
+ for (int j = 0; j < 200; j++) {
+ set[i][j] = false;
+ }
+ }
+}
+
+void dfs(int row, int col, bool set[200][200], int** heights, int rows, int cols) {
+ set[row][col] = true;
+ int a = 0;
+ int b = 0;
+ for (int i = 0; i < 4; i++) {
+ a = directions[i][0] + row;
+ b = directions[i][1] + col;
+ if ((a >= 0) && (a < rows) && (b >= 0) && (b < cols) && (!set[a][b])) {
+ if (heights[a][b] >= heights[row][col]) {
+ dfs(a, b, set, heights, rows, cols);
+ }
+ }
+ }
+}
+
+int** pacificAtlantic(int** heights, int heightsSize, int* heightsColSize, int* returnSize, int** returnColumnSizes) {
+
+ int rows = heightsSize;
+ int cols = heightsColSize[0];
+
+ resetSet(pacific_reach);
+ resetSet(atlantic_reach);
+
+ for (int row = 0; row < rows; row++) {
+ dfs(row, 0, pacific_reach, heights, rows, cols);
+ dfs(row, cols - 1, atlantic_reach, heights, rows, cols);
+ }
+ for (int col = 0; col < cols; col++) {
+ dfs(0, col, pacific_reach, heights, rows, cols);
+ dfs(rows - 1, col, atlantic_reach, heights, rows, cols);
+ }
+
+ int res = 0;
+ for (int row = 0; row < rows; row++) {
+ for (int col = 0; col < cols; col++) {
+ if ((pacific_reach[row][col] == true) && (atlantic_reach[row][col] == true)) {
+ res += 1;
+ }
+ }
+ }
+
+ *returnSize = res;
+ returnColumnSizes[0] = (int*)malloc(res * sizeof(int));
+ for (int i = 0; i < res; i++) {
+ returnColumnSizes[0][i] = 2;
+ }
+
+ int** results = (int**)malloc(res * sizeof(int*));
+ res = 0;
+ for (int row = 0; row < rows; row++) {
+ for (int col = 0; col < cols; col++) {
+ if ((pacific_reach[row][col] == true) && (atlantic_reach[row][col] == true)) {
+ int* buffer = (int*)malloc(2 * sizeof(int));
+ buffer[0] = row;
+ buffer[1] = col;
+ results[res] = buffer;
+ res += 1;
+ }
+ }
+ }
+
+ return results;
+}