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src/main/kotlin/p32xx/Problem3250.kt

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+package p32xx
+
+import util.expect
+
+fun main() {
+    class Solution {
+        fun countOfPairs(nums: IntArray): Int {
+            val m = 1000000007
+
+            var dp = IntArray(51) { if (it <= nums[0]) 1 else 0 }
+
+            for (index in 1 until nums.size) {
+                val newDp = IntArray(51)
+
+                for (cur in 0..nums[index]) {
+                    for (prev in 0..cur) {
+                        if (nums[index - 1] - prev >= nums[index] - cur) {
+                            newDp[cur] = (newDp[cur] + dp[prev]) % m
+                        }
+                    }
+                }
+
+                dp = newDp
+            }
+
+            return dp.fold(0) { sum, c ->
+                (sum + c) % m
+            }
+        }
+    }
+
+    expect {
+        Solution().countOfPairs(
+            intArrayOf()
+        )
+    }
+}