Merge pull request #75 from arunsathiya/solve/42-trapping-rain-water

42. Trapping Rain Water

src/42-trapping-rain-water/main.go

@@ -0,0 +1,25 @@
+package main
+
+func trap(height []int) int {
+	leftMax, rightMax := 0, 0
+	left, right := 0, len(height)-1
+	totalTrap := 0
+	for left < right {
+		if height[left] <= height[right] {
+			if height[left] >= leftMax {
+				leftMax = height[left]
+			} else {
+				totalTrap += leftMax - height[left]
+			}
+			left++
+		} else {
+			if height[right] >= rightMax {
+				rightMax = height[right]
+			} else {
+				totalTrap += rightMax - height[right]
+			}
+			right--
+		}
+	}
+	return totalTrap
+}

src/42-trapping-rain-water/main_test.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"testing"
+)
+
+func TestTrap(t *testing.T) {
+	tests := []struct {
+		height []int
+		want   int
+	}{
+		{
+			height: []int{0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1},
+			want:   6,
+		},
+		{
+			height: []int{4, 2, 0, 3, 2, 5},
+			want:   9,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run("", func(t *testing.T) {
+			got := trap(tt.height)
+			if got != tt.want {
+				t.Errorf("trap(%v) = %v, want %v", tt.height, got, tt.want)
+			}
+		})
+	}
+}