add: 接雨水和买卖股票

Author: Eric-art-coder

src/arr/买卖股票的最佳时机.js

@@ -0,0 +1,46 @@
+function maxProfit(prices) {
+  const len = prices.length;
+  // 创建dp数组
+  const dp = new Array(len).fill([0, 0]);
+  // dp数组初始化
+  dp[0] = [-prices[0], 0];
+  for (let i = 1; i < len; i++) {
+    // 更新dp[i]
+    dp[i] = [
+      Math.max(dp[i - 1][0], -prices[i]),
+      Math.max(dp[i - 1][1], prices[i] + dp[i - 1][0]),
+    ];
+  }
+  return dp[len - 1][1];
+}
+
+console.log(maxProfit([7,1,5,3,6,4])) // 5 
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+// 解法一：贪心
+// let res = 0, low = Infinity
+// for (let i = 0; i < prices.length; i++) {
+//   low = Math.min(low, prices[i])
+//   res = Math.max(res, prices[i] - low)
+// }
+// return res
+
+
+// 解法二：动态规划

src/arr/接雨水.ts

@@ -1,24 +1,25 @@
 // 给定[0,1,0,2,1,0,1,3,2,1,2,1] 
 
 function rain(height) {
-  let left = 0, right = height.length - 1;
-  let leftMax = 0, rightMax = 0, res = 0;
-  while(left < right) {
-    leftMax = Math.max(leftMax, height[left])
-    rightMax = Math.max(rightMax, height[right])
-    if(height[left] < height[right]) {
-      res += leftMax - height[left]
-      left++
+  let leftIndex = 0, rightIndex = height.length - 1;
+  let leftMax = 0, rightMax = 0;
+  let res = 0
+  while(leftIndex < rightIndex) {
+    leftMax = Math.max(leftMax, height[leftIndex])
+    rightMax = Math.max(rightMax, height[rightIndex])
+    if(height[leftIndex] < height[rightIndex]) {
+      res += leftMax - height[leftIndex]
+      leftIndex++
     }else {
-      res += rightMax - height[right]
-      right--
+      res += rightMax - height[rightIndex]
+      rightIndex--
     }
   }
   return res
 }
 
 
-
+console.log(rain([0,1,0,2,1,0,1,3,2,1,2,1])) // 6
 
 
 
@@ -59,4 +60,4 @@ function rain(height) {
 //   return res
 // }
 
-console.log(rain([0,1,0,2,1,0,1,3,2,1,2,1]))
+// console.log(rain([0,1,0,2,1,0,1,3,2,1,2,1]))