diff --git a/problems/0015.三数之和.md b/problems/0015.三数之和.md index e191eabc..9b59e66d 100644 --- a/problems/0015.三数之和.md +++ b/problems/0015.三数之和.md @@ -138,8 +138,12 @@ public: */ if (nums[i] + nums[left] + nums[right] > 0) { right--; + // 当前元素不合适了,可以去重 + while (left < right && nums[right] == nums[right + 1]) right--; } else if (nums[i] + nums[left] + nums[right] < 0) { left++; + // 不合适,去重 + while (left < right && nums[left] == nums[left - 1]) left++; } else { result.push_back(vector{nums[i], nums[left], nums[right]}); // 去重逻辑应该放在找到一个三元组之后 diff --git a/problems/0018.四数之和.md b/problems/0018.四数之和.md index bad258c1..c6c55d50 100644 --- a/problems/0018.四数之和.md +++ b/problems/0018.四数之和.md @@ -91,9 +91,13 @@ public: // nums[k] + nums[i] + nums[left] + nums[right] > target 会溢出 if (nums[k] + nums[i] > target - (nums[left] + nums[right])) { right--; + // 当前元素不合适了,可以去重 + while (left < right && nums[right] == nums[right + 1]) right--; // nums[k] + nums[i] + nums[left] + nums[right] < target 会溢出 } else if (nums[k] + nums[i] < target - (nums[left] + nums[right])) { left++; + // 不合适,去重 + while (left < right && nums[left] == nums[left - 1]) left++; } else { result.push_back(vector{nums[k], nums[i], nums[left], nums[right]}); // 去重逻辑应该放在找到一个四元组之后 diff --git a/problems/0112.路径总和.md b/problems/0112.路径总和.md index a884b278..5db36687 100644 --- a/problems/0112.路径总和.md +++ b/problems/0112.路径总和.md @@ -747,11 +747,132 @@ let pathSum = function(root, targetSum) { }; ``` +## TypeScript + +> 0112.路径总和 + +**递归法:** + +```typescript +function hasPathSum(root: TreeNode | null, targetSum: number): boolean { + function recur(node: TreeNode, sum: number): boolean { + console.log(sum); + if ( + node.left === null && + node.right === null && + sum === 0 + ) return true; + if (node.left !== null) { + sum -= node.left.val; + if (recur(node.left, sum) === true) return true; + sum += node.left.val; + } + if (node.right !== null) { + sum -= node.right.val; + if (recur(node.right, sum) === true) return true; + sum += node.right.val; + } + return false; + } + if (root === null) return false; + return recur(root, targetSum - root.val); +}; +``` + +**递归法(精简版):** + +```typescript +function hasPathSum(root: TreeNode | null, targetSum: number): boolean { + if (root === null) return false; + targetSum -= root.val; + if ( + root.left === null && + root.right === null && + targetSum === 0 + ) return true; + return hasPathSum(root.left, targetSum) || + hasPathSum(root.right, targetSum); +}; +``` + +**迭代法:** + +```typescript +function hasPathSum(root: TreeNode | null, targetSum: number): boolean { + type Pair = { + node: TreeNode, // 当前节点 + sum: number // 根节点到当前节点的路径数值总和 + } + + const helperStack: Pair[] = []; + if (root !== null) helperStack.push({ node: root, sum: root.val }); + let tempPair: Pair; + while (helperStack.length > 0) { + tempPair = helperStack.pop()!; + if ( + tempPair.node.left === null && + tempPair.node.right === null && + tempPair.sum === targetSum + ) return true; + if (tempPair.node.right !== null) { + helperStack.push({ + node: tempPair.node.right, + sum: tempPair.sum + tempPair.node.right.val + }); + } + if (tempPair.node.left !== null) { + helperStack.push({ + node: tempPair.node.left, + sum: tempPair.sum + tempPair.node.left.val + }); + } + } + return false; +}; +``` + +> 0112.路径总和 ii + +**递归法:** + +```typescript +function pathSum(root: TreeNode | null, targetSum: number): number[][] { + function recur(node: TreeNode, sumGap: number, routeArr: number[]): void { + if ( + node.left === null && + node.right === null && + sumGap === 0 + ) resArr.push([...routeArr]); + if (node.left !== null) { + sumGap -= node.left.val; + routeArr.push(node.left.val); + recur(node.left, sumGap, routeArr); + sumGap += node.left.val; + routeArr.pop(); + } + if (node.right !== null) { + sumGap -= node.right.val; + routeArr.push(node.right.val); + recur(node.right, sumGap, routeArr); + sumGap += node.right.val; + routeArr.pop(); + } + } + const resArr: number[][] = []; + if (root === null) return resArr; + const routeArr: number[] = []; + routeArr.push(root.val); + recur(root, targetSum - root.val, routeArr); + return resArr; +}; +``` + ## Swift 0112.路径总和 **递归** + ```swift func hasPathSum(_ root: TreeNode?, _ targetSum: Int) -> Bool { guard let root = root else { diff --git a/problems/前序/广州互联网公司总结.md b/problems/前序/广州互联网公司总结.md index 1cf0da36..e83fcd2b 100644 --- a/problems/前序/广州互联网公司总结.md +++ b/problems/前序/广州互联网公司总结.md @@ -14,6 +14,7 @@ ## 一线互联网 * 微信(总部) 有点难进! +* 字节跳动(广州) ## 二线 * 网易(总部)主要是游戏