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import java.util.Stack;
public class Solution {
    public boolean validateStackSequences(int[] pushed, int[] popped) {
        if (pushed.length != popped.length) {
            return false;
        }
        Stack
   
     stack = new Stack<>();
        int i = 0, j = 0;
        // ???????????????
        while (i < pushed.length) {
            stack.push(pushed[i]);
            i++;
            // ?????????
            if (j < popped.length) {
                if (stack.peek().equals(popped[j])) {
                    stack.pop();
                    j++;
                } else {
                    // ????????????????
                    if (i > 0 && popped[j] == pushed[i - 1]) {
                        stack.pop();
                        j++;
                    } else {
                        // ?????????
                        return false;
                    }
                }
            }
        }
        // ?????????
        while (j < popped.length) {
            if (stack.isEmpty()) {
                return false;
            }
            if (stack.peek() != popped[j]) {
                return false;
            }
            stack.pop();
            j++;
        }
        return true;
    }
}
   

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