【easy】278. First Bad Version
阿新 • • 發佈:2018-02-12
api 產品 div higher first other 給定 int 猜數遊戲
有一系列產品,從某個開始其後都不合格,給定一個判斷是否合格的函數,找出N個產品中第一個不合格的產品。
正確答案:
// Forward declaration of isBadVersion API. bool isBadVersion(int version); class Solution { public: int firstBadVersion(int n) { int low = 1; int high = n; int ver = 0; while (low < high) { ver= low + (high - low) / 2; //這個題註意點!!如果直接high+low可能溢出,就會超時…… if (isBadVersion(ver)) { high = ver; } else { low = ver + 1; } } return low; } };
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有一道非常類似的題目
猜數遊戲:1-n之內有一個數是預選的數字,每次回告訴大還是小或者正確。返回猜中的數字。
// Forward declaration of guess API. // @param num, your guess // @return -1 if my number is lower, 1 if my number is higher, otherwise return 0 int guess(int num); class Solution { public: int guessNumber(int n) { int start = 1; int end = n; int res = 1; while (start<end){int mid = start + (end-start)/2; if (guess(mid)==0){ return mid; } if (guess(mid)==1) start = mid+1; else end = mid-1; } if (guess(start)) return start; return end; } };
【easy】278. First Bad Version