feat: add solutions to lcp problem: No.28

Author: yanglbme

lcp/LCP 28. 采购方案/README.md

@@ -43,15 +43,77 @@
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
 ```python
-
+class Solution:
+    def purchasePlans(self, nums: List[int], target: int) -> int:
+        nums.sort()
+        i, j = 0, len(nums) - 1
+        res = 0
+        while i < j:
+            if nums[i] + nums[j] > target:
+                j -= 1
+            else:
+                res += (j - i)
+                i += 1
+        return res % 1000000007
 ```
 
 ### **Java**
 
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
 ```java
+class Solution {
+    public int purchasePlans(int[] nums, int target) {
+        Arrays.sort(nums);
+        int res = 0, mod = 1000000007;
+        for (int i = 0, j = nums.length - 1; i < j; ++i) {
+            while (i < j && nums[i] + nums[j] > target) {
+                --j;
+            }
+            if (i < j) {
+                res = (res + j - i) % mod;
+            }
+        }
+        return res;
+    }
+}
+```
+
+### **C++**
+
+```cpp
+class Solution {
+public:
+    int purchasePlans(vector<int>& nums, int target) {
+        const int MOD = 1000000007;
+        sort(nums.begin(), nums.end());
+        int res = 0;
+        for (int i = 0, j = nums.size() - 1; i < j; ++i)
+        {
+            while (i < j && nums[i] + nums[j] > target) --j;
+            if (i < j)  res = (res + j - i) % MOD;
+        }
+        return res;
+    }
+};
+```
 
+### **Go**
+
+```go
+func purchasePlans(nums []int, target int) int {
+	sort.Ints(nums)
+	res, mod := 0, 1000000007
+	for i, j := 0, len(nums)-1; i < j; i++ {
+		for i < j && nums[i]+nums[j] > target {
+			j--
+		}
+		if i < j {
+			res = (res + j - i) % mod
+		}
+	}
+	return res
+}
 ```
 
 ### **...**

lcp/LCP 28. 采购方案/Solution.cpp

@@ -0,0 +1,14 @@
+class Solution {
+public:
+    int purchasePlans(vector<int>& nums, int target) {
+        const int MOD = 1000000007;
+        sort(nums.begin(), nums.end());
+        int res = 0;
+        for (int i = 0, j = nums.size() - 1; i < j; ++i)
+        {
+            while (i < j && nums[i] + nums[j] > target) --j;
+            if (i < j)  res = (res + j - i) % MOD;
+        }
+        return res % MOD;
+    }
+};

lcp/LCP 28. 采购方案/Solution.go

@@ -0,0 +1,13 @@
+func purchasePlans(nums []int, target int) int {
+	sort.Ints(nums)
+	res, mod := 0, 1000000007
+	for i, j := 0, len(nums)-1; i < j; i++ {
+		for i < j && nums[i]+nums[j] > target {
+			j--
+		}
+		if i < j {
+			res = (res + j - i) % mod
+		}
+	}
+	return res
+}

lcp/LCP 28. 采购方案/Solution.java

@@ -0,0 +1,15 @@
+class Solution {
+    public int purchasePlans(int[] nums, int target) {
+        Arrays.sort(nums);
+        int res = 0, mod = 1000000007;
+        for (int i = 0, j = nums.length - 1; i < j; ++i) {
+            while (i < j && nums[i] + nums[j] > target) {
+                --j;
+            }
+            if (i < j) {
+                res = (res + j - i) % mod;
+            }
+        }
+        return res % mod;
+    }
+}

lcp/LCP 28. 采购方案/Solution.py

@@ -0,0 +1,12 @@
+class Solution:
+    def purchasePlans(self, nums: List[int], target: int) -> int:
+        nums.sort()
+        i, j = 0, len(nums) - 1
+        res = 0
+        while i < j:
+            if nums[i] + nums[j] > target:
+                j -= 1
+            else:
+                res += (j - i)
+                i += 1
+        return res % 1000000007