add new solutions

solutions/18/q1877/solution.go

@@ -0,0 +1,16 @@
+package q1877
+
+import "slices"
+
+func minPairSum(nums []int) int {
+	slices.Sort(nums)
+	n := len(nums)
+
+	maxSum := 0
+	for i := range n / 2 {
+		maxSum = max(maxSum, nums[i]+nums[n-1-i])
+	}
+	return maxSum
+}
+
+var _ = minPairSum

solutions/18/q1895/solution.go

@@ -0,0 +1,59 @@
+package q1895
+
+func isMagicSq(grid [][]int, x, y, w int) bool {
+	diag1Sum := 0
+	diag2Sum := 0
+	for i := range w {
+		ax, ay := x+i, y+i
+		diag1Sum += grid[ay][ax]
+		ax = x + w - 1 - i
+		diag2Sum += grid[ay][ax]
+	}
+	if diag1Sum != diag2Sum {
+		return false
+	}
+
+	// horizontal
+	for dy := range w {
+		sum := 0
+		for dx := range w {
+			sum += grid[y+dy][x+dx]
+		}
+		if sum != diag1Sum {
+			return false
+		}
+	}
+	// vertical
+	for dx := range w {
+		sum := 0
+		for dy := range w {
+			sum += grid[y+dy][x+dx]
+		}
+		if sum != diag1Sum {
+			return false
+		}
+	}
+
+	return true
+}
+
+func largestMagicSquare(grid [][]int) int {
+	k := 1
+	gW, gH := len(grid[0]), len(grid)
+
+Outer:
+	for w := 2; w <= min(gW, gH); w++ {
+		for y := range gH - w + 1 {
+			for x := range gW - w + 1 {
+				if isMagicSq(grid, x, y, w) {
+					k = w
+					continue Outer
+				}
+
+			}
+		}
+	}
+	return k
+}
+
+var _ = largestMagicSquare