feat: 2025-10-28打卡

122.best-time-to-buy-and-sell-stock-ii.java

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+/*
+ * @lc app=leetcode id=122 lang=java
+ *
+ * [122] Best Time to Buy and Sell Stock II
+ */
+
+// @lc code=start
+class Solution {
+    public int maxProfit(int[] prices) {
+        if(prices == null || prices.length <= 1) {
+            return 0;
+        }
+        int total = 0;
+        for(int i = 1; i<prices.length; i++) {
+            if(prices[i] - prices[i-1] > 0) {
+                total += prices[i] - prices[i-1];
+            }
+        }
+        return total;
+    }
+}
+// @lc code=end
+

134.gas-station.java

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+/*
+ * @lc app=leetcode id=134 lang=java
+ *
+ * [134] Gas Station
+ */
+
+// @lc code=start
+class Solution {
+    /**
+     * 本题核心为：若从i开始，计算到j时发现不行，那么从(i, j]范围内任一站点开始也不行，易进行论证
+     * 
+     * @param gas
+     * @param cost
+     * @return
+     */
+    public int canCompleteCircuit(int[] gas, int[] cost) {
+        int start = 0, sum = 0, curIdx = 0;
+        while(start < gas.length) {
+            if(curIdx - start == gas.length) {
+                return start;
+            }
+            int pos = curIdx % gas.length;
+            if(sum + gas[pos] - cost[pos] < 0) {
+                curIdx++;
+                start = curIdx;
+                sum = 0;
+            } else {
+                sum += gas[pos] - cost[pos];
+                curIdx++;
+            }
+        }
+        return -1;
+    }
+}
+// @lc code=end
+

14.longest-common-prefix.java

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+/*
+ * @lc app=leetcode id=14 lang=java
+ *
+ * [14] Longest Common Prefix
+ */
+
+// @lc code=start
+class Solution {
+    public String longestCommonPrefix(String[] strs) {
+        if(strs == null || strs.length == 0) {
+            return "";
+        }
+        String r = strs[0];
+        for(int i=1; i<strs.length;i++) {
+            r = longestCommonPrefix(r, strs[i]);
+        }
+        return r;
+    }
+
+    private String longestCommonPrefix(String a, String b) {
+        StringBuilder sb = new StringBuilder();
+        for(int i = 0; i<a.length() && i<b.length();i++) {
+            if(a.charAt(i) != b.charAt(i)) {
+                break;
+            }
+            sb.append(a.charAt(i));
+        }
+        return sb.toString();
+    }
+}
+// @lc code=end
+

55.jump-game.java

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+/*
+ * @lc app=leetcode id=55 lang=java
+ *
+ * [55] Jump Game
+ */
+
+// @lc code=start
+class Solution {
+    public boolean canJump(int[] nums) {
+        int cur = 0;
+        for(int i=0;i<nums.length;i++) {
+            if(i > cur) {
+                return false;
+            }
+            if(nums[i]>0) {
+                cur = Math.max(cur, i+nums[i]);
+            }
+        }
+        return true;
+    }
+}
+// @lc code=end
+