利用遗传算法求最小值，程序中求得是表达式x1*x1+x2*x2+x3*x3再-2~2上的最小值，以及对应的x值，算法中使用二进制编码，交叉采用不同交叉和优势交叉，变异也分两种，不用变异和优势变异-using genetic algorithms for the minimum, procedures to seek expressions x1 x1 x2*** x2 x3 x3 another 2 ~ 2 on the minimum, and the corresponding value of x, algorithm using binary encoding, using different cross-cross and advantages of crossover and mutation at the two without variation and variation advantage