二分写法

二分的正确写法

整数二分

int l = 0, r = n;while (l <= r) {    int nMid = (l + r) >> 1;    if (Judge(x, y, nMid)) {        l = nMid + 1;    }    else {        r = nMid - 1;    }}//注意当l为0时, 输出0, 而非-1cout << l - 1 << endl;

实数二分

double l = 0, r = n;//精度具体看题意while (r - l > 0.0001) {    double nMid = (l + r) / 2.0;    if (Judge(x, y, nMid)) {        l = nMid;    }    else {        r = nMid;    }}cout << l << endl;