add new solutions

solutions/18/q1878/solution.go

@@ -0,0 +1,75 @@
+// Package q1878 implements a solution for https://leetcode.com/problems/get-biggest-three-rhombus-sums-in-a-grid/
+package q1878
+
+import "slices"
+
+func getBiggestThree(grid [][]int) []int {
+	w, h := len(grid[0]), len(grid)
+	sums := make([][][2]int, h)
+	sums[0] = make([][2]int, w*h)
+	for s := h - 1; s >= 0; s-- {
+		sums[s] = sums[0][s*w : (s+1)*w]
+	}
+
+	for r := range h {
+		for c := range w {
+			pR, pC := r-1, c-1
+			if pR >= 0 && pC >= 0 {
+				sums[r][c][0] = sums[pR][pC][0] + grid[r][c]
+			} else {
+				sums[r][c][0] = grid[r][c]
+			}
+
+			pR, pC = r-1, c+1
+			if pR >= 0 && pC < w {
+				sums[r][c][1] = sums[pR][pC][1] + grid[r][c]
+			} else {
+				sums[r][c][1] = grid[r][c]
+			}
+		}
+	}
+
+	biggest := []int{0, 0, 0, 0}
+	var addResult = func(val int) {
+		for i := 1; i <= 3; i++ {
+			if biggest[i] == val {
+				return
+			}
+		}
+		biggest[0] = val
+		slices.Sort(biggest)
+	}
+
+	var isValid = func(coord [2]int) bool {
+		return coord[0] >= 0 && coord[1] >= 0 && coord[0] < h && coord[1] < w
+	}
+
+	for r := range h {
+		for c := range w {
+			addResult(grid[r][c])
+
+			for edge := 2; ; edge++ {
+				left := [2]int{r + edge - 1, c - edge + 1}
+				right := [2]int{r + edge - 1, c + edge - 1}
+				bottom := [2]int{r + (edge-1)*2, c}
+				if !isValid(left) || !isValid(right) || !isValid(bottom) {
+					break
+				}
+
+				e1 := sums[left[0]][left[1]][1] - sums[r][c][1]
+				e2 := sums[bottom[0]][bottom[1]][0] - sums[left[0]][left[1]][0]
+				e3 := sums[bottom[0]][bottom[1]][1] - sums[right[0]][right[1]][1]
+				e4 := sums[right[0]][right[1]][0] - sums[r][c][0]
+				addResult(e1 + e2 + e3 + e4 - grid[bottom[0]][bottom[1]] + grid[r][c])
+			}
+		}
+	}
+
+	for biggest = biggest[1:]; biggest[0] == 0; {
+		biggest = biggest[1:]
+	}
+	slices.Reverse(biggest)
+	return biggest
+}
+
+var _ = getBiggestThree