第四周作业#33

Week_04/id_33/Leetcode_46_33.java

@@ -0,0 +1,27 @@
+/*
+ * @lc app=leetcode id=46 lang=java
+ *
+ * [46] Permutations
+ */
+class Solution {
+    public List<List<Integer>> permute(int[] nums) {
+        List<List<Integer>> result = new ArrayList<>();
+        backTrace(nums, result, new ArrayList<>());
+        return result;
+    }
+
+    public void backTrace(int[] nums, List<List<Integer>> result, List<Integer> tempList){
+        if(tempList.size() == nums.length){
+            result.add(new ArrayList<Integer>(tempList));
+            return;
+        }
+
+        for(int i = 0; i< nums.length; i++){
+            if(tempList.contains(nums[i])) continue;
+            tempList.add(nums[i]);
+            backTrace(nums, result, tempList);
+            tempList.remove(tempList.size()-1);
+        }
+    }
+}
+

Week_04/id_33/Leetcode_53_33.java

@@ -0,0 +1,17 @@
+/*
+ * @lc app=leetcode id=53 lang=java
+ *
+ * [53] Maximum Subarray
+ */
+class Solution {
+    public int maxSubArray(int[] nums) {
+        if(nums.length==0) return 0;
+        int maxSum = nums[0], sum = nums[0];
+        for (int i = 1; i < nums.length; i++){
+            sum = Math.max(nums[i], sum + nums[i]);
+            maxSum = Math.max(sum, maxSum);
+        }
+        return maxSum;
+    }
+}
+

Week_04/id_33/Leetcode_62_33.java

@@ -0,0 +1,19 @@
+/*
+ * @lc app=leetcode id=62 lang=java
+ *
+ * [62] Unique Paths
+ */
+class Solution {
+    public int uniquePaths(int m, int n) {
+        int[][] dp = new int[n][m];
+        for (int i = 0; i < n; i++) dp[i][0] = 1;
+        for (int i = 0; i < m; i++) dp[0][i] = 1;
+        for (int i = 1; i < n; i++){
+            for (int j = 1; j < m; j++){
+                dp[i][j] = dp[i-1][j] + dp[i][j-1];
+            }
+        }
+        return dp[n-1][m-1];
+    }
+}
+

Week_04/id_33/Leetcode_70_33.java

@@ -0,0 +1,18 @@
+/*
+ * @lc app=leetcode id=70 lang=java
+ *
+ * [70] Climbing Stairs
+ */
+class Solution {
+    public int climbStairs(int n) {
+        if (n == 1) return 1;
+        int[] dp = new int[n + 1];
+        dp[1] = 1;
+        dp[2] = 2;
+        for (int i = 3; i <= n; i++) {
+            dp[i] = dp[i - 1] + dp[i - 2];
+        }
+        return dp[n];
+    }
+}
+

Week_04/id_33/Leetcode_714_33.java

@@ -0,0 +1,21 @@
+/*
+ * @lc app=leetcode id=714 lang=java
+ *
+ * [714] Best Time to Buy and Sell Stock with Transaction Fee
+ */
+class Solution {
+    public int maxProfit(int[] prices, int fee) {
+        if(prices.length <= 1) return 0;
+		int profit = 0, min = prices[0];
+		for(int i = 0;i < prices.length;i++){
+			if(prices[i] < min){
+				min = prices[i];
+			}else if(prices[i] > min + fee){
+				profit += prices[i] - min - fee;
+				min = prices[i] - fee;
+			}
+		}
+		return profit;
+    }
+}
+