Problem 223: Rectangle area

problems/223-rectangle-area/Makefile

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+all: lib.o main.o
+	gcc -Wall -o bin lib.o main.o
+
+lib.o: lib.c
+	gcc -c -Wall lib.c
+
+main.o: main.c
+	gcc -c -Wall main.c
+
+run:
+	./bin
+
+clean:
+	rm *.o bin

problems/223-rectangle-area/lib.c

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+#include "lib.h"
+
+int _findIntersection(int a_start, int a_end, int b_start, int b_end) {
+    // aaaa
+    //   bbbb
+    if (a_end > b_start && a_start <= b_start && a_end <= b_end)
+        return a_end - b_start;
+    //   aa
+    // bbbbbb
+    if (a_start >= b_start && a_end <= b_end)
+        return a_end - a_start;
+    //   aaaa
+    // bbbb
+    if (a_start >= b_start && a_start < b_end && a_end >= b_end)
+        return b_end - a_start;
+    // aaaaa
+    //  bb
+    if (b_start >= a_start && b_end <= a_end)
+        return b_end - b_start;
+    return 0;
+}
+
+int computeArea(int ax1, int ay1, int ax2, int ay2, int bx1, int by1, int bx2, int by2) {
+    // Area of the first rectangle
+    int a = (ax2 - ax1) * (ay2 - ay1);
+
+    // Area of the second rectangle
+    int b = (bx2 - bx1) * (by2 - by1);
+
+    // Find intersection
+    int x_intersection = _findIntersection(ax1, ax2, bx1, bx2);
+    int y_intersection = _findIntersection(ay1, ay2, by1, by2);
+
+    return a + b - x_intersection * y_intersection;
+}

problems/223-rectangle-area/lib.h

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+#pragma once
+int computeArea(int ax1, int ay1, int ax2, int ay2, int bx1, int by1, int bx2, int by2);

problems/223-rectangle-area/main.c

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+#include <stdio.h>
+#include "lib.h"
+
+int main() {
+    int res1 = computeArea(-3, 0, 3, 4, 0, -1, 9, 2);
+    printf("Test 1: %d\n", res1 == 45);
+
+    int res2 = computeArea(-2, -2, 2, 2, -2, -2, 2, 2);
+    printf("Test 2: %d\n", res2 == 16);
+
+    return 0;
+}

problems/223-rectangle-area/readme.md

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+# 223. Rectangle area
+
+[Leetcode](https://leetcode.com/problems/rectangle-area/)
+
+Given the coordinates of two rectilinear rectangles in a 2D plane,
+return the total area covered by the two rectangles.
+
+The first rectangle is defined by its
+bottom-left corner (ax1, ay1) and its
+top-right corner (ax2, ay2).
+
+The second rectangle is defined by its
+bottom-left corner (bx1, by1) and its
+top-right corner (bx2, by2).