mso-text-raise: -3.0pt">R</span></sup></span><span style="font-family: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"><font size="3">为</font></span><span lang="EN-US"><span style="position: relative; top: 3pt; mso-text-raise: -3.0pt">W</span></span><span style="font-family: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"><font size="3">反序后的字符串。先给定字符串S</font></span><span style="font-family: 