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-rw-r--r--maximal_rectangle.c62
1 files changed, 62 insertions, 0 deletions
diff --git a/maximal_rectangle.c b/maximal_rectangle.c
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+// 85. Maximal Rectangle
+#include "leetcode.h"
+
+/*
+ * given a 'rows * cols' binary 'matrix' filled with 0's and 1's, find the
+ * largest rectangle containing only 1's and return its area.
+ */
+
+int max_area(int *heights, int heights_size) {
+ int *stack = (int *)malloc(heights_size * sizeof(int));
+ int depth = 0, width = 0, res = 0, i = 0, tmp = 0;
+ if (!heights || !heights_size)
+ return 0;
+ while (i < heights_size) {
+ if (!depth || heights[i] >= heights[stack[depth - 1]]) {
+ stack[depth] = i;
+ depth++, i++;
+ } else {
+ while (depth && heights[stack[depth - 1]] > heights[i]) {
+ width = depth > 1 ? i - stack[depth - 2] - 1 : i;
+ tmp = heights[stack[depth - 1]] * width;
+ if (res < tmp)
+ res = tmp;
+ depth--;
+ }
+ }
+ }
+ while (depth) {
+ width = depth > 1 ? i - stack[depth - 2] - 1 : i;
+ tmp = heights[stack[depth - 1]] * width;
+ if (res < tmp)
+ res = tmp;
+ depth--;
+ }
+ free(stack);
+ return res;
+}
+
+int maximalRectangle(char **matrix, int matrix_size, int *matrix_col_size) {
+ int *heights = (int *)calloc(*matrix_col_size, sizeof(int));
+ int ans = 0;
+ if (!matrix || !matrix_size)
+ return 0;
+ for (int i = 0; i < matrix_size; i++) {
+ for (int j = 0; j < *matrix_col_size; j++)
+ heights[j] = matrix[i][j] == '0' ? 0 : heights[j] + 1;
+ int tmp = max_area(heights, *matrix_col_size);
+ if (ans < tmp)
+ ans = tmp;
+ }
+ free(heights);
+ return ans;
+}
+
+int main() {
+ char *matrix[4][5] = {{"1", "0", "1", "0", "0"},
+ {"1", "0", "1", "1", "1"},
+ {"1", "1", "1", "1", "1"},
+ {"1", "0", "0", "1", "0"}};
+ int matrix_col_size = 5;
+ printf("%d\n", maximalRectangle((char **)matrix, 4, &matrix_col_size));
+}