构造对偶式是解竞赛题时常用的一种解题技巧,对于一些较难的问题,如果拘泥于常规解法,常常需要进行繁琐的运算而且容易出错,若能从题设条件和所求结论的特点出发,构造与之相关的对偶式,将问题转化为所构造的对偶式来确定,可以收到峰回路转、化难为易的功效·一、利用奇偶关系构 Constructing duality is a commonly used problem-solving technique for solving competition problems. For some difficult problems, if you are stuck with conventional solutions, you often need to perform tedious operations and are prone to errors. If you can set the conditions and the conclusions Starting from the characteristics, construct the related duality, and convert the problem into the duality of the structure to be determined. It can receive the effect of the peak-turn and turn-around. First, use the odd-even relationship.