题解 | #单调栈#
单调栈
http://www.nowcoder.com/practice/ae25fb47d34144a08a0f8ff67e8e7fb5
import java.util.*;
public class Solution {
/**
* 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
*
*
* @param nums int一维数组
* @return int二维数组
*/
public int[][] foundMonotoneStack (int[] nums) {
// write code here
int len = nums.length;
int[][] matrix = new int[len][2];
Stack stack = new Stack<>();
for(int i = 0;i < len;i ++){
if(stack.isEmpty()) {
stack.push(i);
matrix[i][0] = -1;
}else if(nums[stack.peek()] < nums[i]){
matrix[i][0] = stack.peek();
stack.push(i);
}else{
while(!stack.isEmpty() && nums[stack.peek()] >= nums[i]){
stack.pop();
}
if(stack.isEmpty()) {
stack.push(i);
matrix[i][0] = -1;
}else{
matrix[i][0] = stack.peek();
stack.push(i);
}
}
}
stack.clear();
for(int i = len -1;i >= 0;i --){
if(stack.isEmpty()) {
stack.push(i);
matrix[i][1] = -1;
}else if(nums[stack.peek()] < nums[i]){
matrix[i][1] = stack.peek();
stack.push(i);
}else{
while(!stack.isEmpty() && nums[stack.peek()] >= nums[i]){
stack.pop();
}
if(stack.isEmpty()) {
stack.push(i);
matrix[i][1] = -1;
}else{
matrix[i][1] = stack.peek();
stack.push(i);
}
}
}
return matrix;
}
}
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