数组a为[3,6,1,4,2,3,7,5,8], 则打印[-1,3,-1,1,1,2,3,3,5]。单调栈：array = [] array必须从小到大有序保存结果：res = []1.3入栈 array = [3] res[0] = -12.6入栈 array = [3,6] res[1] = 33.1入栈 3，6出栈 array = [1], res[2]= -14.4入栈 array = [1,4], res[3] = 15.2入栈 4出栈 array = [1,2], res[4] = 16.3入栈 array = [1,2,3] res[5] = 27.7入栈 array = [1,2,3,7] res[6] = 38.5入栈 7出栈 array = [1,2,3,5] res[7] = 39.8入栈 array = [1,2,3,5,8] res[8] = 5res = [-1, 3, -1, 1, 1, 2, 3, 3, 5]