91 lines
2.7 KiB
Java
91 lines
2.7 KiB
Java
//给定 pushed 和 popped 两个序列，每个序列中的 值都不重复，只有当它们可能是在最初空栈上进行的推入 push 和弹出 pop 操作序列的结果时
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//，返回 true；否则，返回 false 。
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//
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//
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//
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// 示例 1：
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//
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// 输入：pushed = [1,2,3,4,5], popped = [4,5,3,2,1]
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//输出：true
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//解释：我们可以按以下顺序执行：
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//push(1), push(2), push(3), push(4), pop() -> 4,
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//push(5), pop() -> 5, pop() -> 3, pop() -> 2, pop() -> 1
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//
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//
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// 示例 2：
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//
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// 输入：pushed = [1,2,3,4,5], popped = [4,3,5,1,2]
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//输出：false
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//解释：1 不能在 2 之前弹出。
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//
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//
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//
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//
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// 提示：
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//
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//
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// 0 <= pushed.length == popped.length <= 1000
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// 0 <= pushed[i], popped[i] < 1000
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// pushed 是 popped 的排列。
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//
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// Related Topics 栈
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// 👍 175 👎 0
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package leetcode.editor.cn;
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import java.util.Stack;
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//946:验证栈序列
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public class ValidateStackSequences {
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public static void main(String[] args) {
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//测试代码
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Solution solution = new ValidateStackSequences().new Solution();
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//true
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System.out.println(solution.validateStackSequences(new int[]{1, 2, 3, 4, 5}, new int[]{4, 5, 3, 2, 1}));
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//false
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System.out.println(solution.validateStackSequences(new int[]{1, 2, 3, 4, 5}, new int[]{4, 3, 5, 1, 2}));
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}
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//力扣代码
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//leetcode submit region begin(Prohibit modification and deletion)
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class Solution {
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public boolean validateStackSequences(int[] pushed, int[] popped) {
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Stack<Integer> stack = new Stack<>();
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int j = 0;
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for (int i = 0; i < popped.length; i++) {
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if (j == pushed.length) {
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return false;
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}
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while (j < pushed.length && popped[i] != pushed[j]) {
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stack.push(pushed[j]);
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j++;
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if (j == pushed.length) {
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return false;
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}
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}
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j++;
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while (!stack.isEmpty() && i < popped.length - 1 && popped[i + 1] == stack.peek()) {
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stack.pop();
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i++;
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}
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}
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return true;
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// // 官方
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// int N = pushed.length;
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// Stack<Integer> stack = new Stack<>();
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//
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// int j = 0;
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// for (int x : pushed) {
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// stack.push(x);
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// while (!stack.isEmpty() && j < N && stack.peek() == popped[j]) {
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// stack.pop();
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// j++;
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// }
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// }
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//
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// return j == N;
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}
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}
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//leetcode submit region end(Prohibit modification and deletion)
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} |