Trap water

Signed-off-by: Leo Ma <[email protected]>

042_trapping_rain_water/Makefile

@@ -0,0 +1,2 @@
+all:
+	gcc -O2 -o test trap_water.c

042_trapping_rain_water/trap_water.c

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+#include <stdio.h>
+#include <stdlib.h>
+
+static int trap(int* height, int heightSize) {
+    if (heightSize < 2) {
+        return 0;
+    }
+
+    int i, j, top0 = -1, top1 = -1, sum = 0, level = 0;
+    for (i = 0; i < heightSize; i++) {
+        if (height[i] > 0) {
+            top0 = i;
+            break;
+        }
+    }
+
+    while (i < heightSize) {
+        top1 = -1;
+        for (j = i + 1; j < heightSize; j++) {
+            if (height[j] >= height[j - 1]) {
+                if (top1 < 0 || height[j] >= height[top1]) {
+                    top1 = j;
+                }
+                if (height[j] >= height[top0]) {
+                    break;
+                }
+            }
+        }
+
+        if (top1 >= 0) {
+            int level = height[top0] < height[top1] ? height[top0] : height[top1];
+            while (i < top1) {
+                if (level > height[i]) {
+                    sum += level - height[i];
+                }
+                i++;
+            }
+            top0 = top1;
+            i = top1;
+        } else {
+            i = j;
+        }
+    }
+
+    return sum;
+}
+
+int main(int argc, char **argv)
+{
+    int i, count = argc - 1;
+    int *nums = malloc(count * sizeof(int));
+    for (i = 0; i < count; i++) {
+        nums[i] = atoi(argv[i + 1]);
+    }
+    printf("%d\n", trap(nums, count));
+    return 0;
+}