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先分類 先計算首位是偶數的情況 那麼百位有2種選擇2,4(0不能做百位哦)然後在選個位~有2中選擇(一共三個偶數,被選走了一個做百位)最後選十位還有4種選擇 這樣百位是偶數的有2*2*4=16個數 百位是奇數的話有3種選擇(1,3,5),各位必須是偶數也有三種選擇(0,2,4),十位隨便又是三種 這樣百位是奇數的有3*3*4=36個數 總共有52個數
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