• Include instructions on updating conda in the main README.md. (#13343) Other • Add a lighter weight s3 test; update embedded test package index. (#13085) • Refactor code to use lazy imports for all other purposes (#8738) Deprecations/Breaking Changes • The --prune flag no longer does anything. Pruning is implicitly the standard behavior now as a result of the initial solver specs coming from explicitly #1749 • add dependencies even if strictness == 3, #1766 4.4.179 3.18.3 (2015-10-15) • added a pruning step for more efficient solves, #1702 • disallow conda-env to be installed into non-root environment

• Include instructions on updating conda in the main README.md. (#13343) Other • Add a lighter weight s3 test; update embedded test package index. (#13085) • Refactor code to use lazy imports for all other purposes (#8738) Deprecations/Breaking Changes • The --prune flag no longer does anything. Pruning is implicitly the standard behavior now as a result of the initial solver specs coming from explicitly #1749 • add dependencies even if strictness == 3, #1766 4.4.182 3.18.3 (2015-10-15) • added a pruning step for more efficient solves, #1702 • disallow conda-env to be installed into non-root environment

• Include instructions on updating conda in the main README.md. (#13343) Other • Add a lighter weight s3 test; update embedded test package index. (#13085) • Refactor code to use lazy imports for all other purposes (#8738) Deprecations/Breaking Changes • The --prune flag no longer does anything. Pruning is implicitly the standard behavior now as a result of the initial solver specs coming from explicitly #1749 • add dependencies even if strictness == 3, #1766 4.4.183 3.18.3 (2015-10-15) • added a pruning step for more efficient solves, #1702 • disallow conda-env to be installed into non-root environment

• Include instructions on updating conda in the main README.md. (#13343) Other • Add a lighter weight s3 test; update embedded test package index. (#13085) • Refactor code to use lazy imports for all other purposes (#8738) Deprecations/Breaking Changes • The --prune flag no longer does anything. Pruning is implicitly the standard behavior now as a result of the initial solver specs coming from explicitly #1749 • add dependencies even if strictness == 3, #1766 4.4.184 3.18.3 (2015-10-15) • added a pruning step for more efficient solves, #1702 • disallow conda-env to be installed into non-root environment

• Include instructions on updating conda in the main README.md. (#13343) Other • Add a lighter weight s3 test; update embedded test package index. (#13085) • Refactor code to use lazy imports for all other purposes (#8738) Deprecations/Breaking Changes • The --prune flag no longer does anything. Pruning is implicitly the standard behavior now as a result of the initial solver specs coming from explicitly #1749 • add dependencies even if strictness == 3, #1766 4.4.185 3.18.3 (2015-10-15) • added a pruning step for more efficient solves, #1702 • disallow conda-env to be installed into non-root environment

• Include instructions on updating conda in the main README.md. (#13343) Other • Add a lighter weight s3 test; update embedded test package index. (#13085) • Refactor code to use lazy imports for all other purposes (#8738) Deprecations/Breaking Changes • The --prune flag no longer does anything. Pruning is implicitly the standard behavior now as a result of the initial solver specs coming from explicitly #1749 • add dependencies even if strictness == 3, #1766 4.4.196 3.18.3 (2015-10-15) • added a pruning step for more efficient solves, #1702 • disallow conda-env to be installed into non-root environment

• Include instructions on updating conda in the main README.md. (#13343) Other • Add a lighter weight s3 test; update embedded test package index. (#13085) • Refactor code to use lazy imports for all other purposes (#8738) Deprecations/Breaking Changes • The --prune flag no longer does anything. Pruning is implicitly the standard behavior now as a result of the initial solver specs coming from explicitly #1749 • add dependencies even if strictness == 3, #1766 4.4.194 3.18.3 (2015-10-15) • added a pruning step for more efficient solves, #1702 • disallow conda-env to be installed into non-root environment

• Include instructions on updating conda in the main README.md. (#13343) Other • Add a lighter weight s3 test; update embedded test package index. (#13085) • Refactor code to use lazy imports for all other purposes (#8738) Deprecations/Breaking Changes • The --prune flag no longer does anything. Pruning is implicitly the standard behavior now as a result of the initial solver specs coming from explicitly #1749 • add dependencies even if strictness == 3, #1766 4.4.190 3.18.3 (2015-10-15) • added a pruning step for more efficient solves, #1702 • disallow conda-env to be installed into non-root environment

• Include instructions on updating conda in the main README.md. (#13343) Other • Add a lighter weight s3 test; update embedded test package index. (#13085) • Refactor code to use lazy imports for all other purposes (#8738) Deprecations/Breaking Changes • The --prune flag no longer does anything. Pruning is implicitly the standard behavior now as a result of the initial solver specs coming from explicitly #1749 • add dependencies even if strictness == 3, #1766 4.4.187 3.18.3 (2015-10-15) • added a pruning step for more efficient solves, #1702 • disallow conda-env to be installed into non-root environment

（backtracking） 回退指遇到不满足约束条件的状态时，撤销前面做 出的选择，回到上一个状态 当越过叶节点、结束节点访问、遇到值为 3 的 节点时终止搜索，函数返回 剪枝 （pruning） 剪枝是根据问题特性和约束条件避免无意义的搜索 路径的方法，可提高搜索效率 当遇到值为 3 的节点时，则不再继续搜索 第 13 章 回溯 hello‑algo.com 281 Tip KnapsackDFS(int[] weight, int[] val, int i, int c) { // 若已选完所有物品或背包无剩余容量，则返回价值 0 if (i == 0 || c == 0) { return 0; } // 若超过背包容量，则只能选择不放入背包 if (weight[i - 1] > c) { return KnapsackDFS(weight, val, i - 1 1, c); } // 计算不放入和放入物品 i 的最大价值 int no = KnapsackDFS(weight, val, i - 1, c); int yes = KnapsackDFS(weight, val, i - 1, c - weight[i - 1]) + val[i - 1]; // 返回两种方案中价值更大的那一个 return Math.Max(no, yes);