《Cracking the Coding Interview》——第11章：排序和搜索——题目5

2014-03-21 21:37

题目：给定一个字符串数组，但是其中夹杂了很多空串“”，不如{“Hello”, “”, “World”, “”, “”, “”, “Zoo”, “”}请设计一个算法在其中查找字符串。

解法：要么一次性将其中夹杂的空串去掉，要么在二分查找的过程中逐个跳过空串。反正整体思路仍是二分。

代码：

// 11.5 Given an array of strings interspersed with empty string ""s. Find out if a target string exists in the string.
#include <iostream>
#include <string>
#include <vector>
using namespace std;

int main()
{
    int i, j, n;
    int ns;
    string s;
    vector<string> v;
    int ll, rr, mm;
    
    while (cin >> n && n > 0) {
        cin >> ns;
        for (i = 0; i < ns; ++i) {
            v.push_back("");
        }
        for (i = 0; i < n; ++i) {
            cin >> s;
            v.push_back(s);
            cin >> ns;
            for (j = 0; j < ns; ++j) {
                v.push_back("");
            }
        }
        cin >> s;
        
        ll = 0;
        while (v[ll] == "") {
            ++ll;
        }
        rr = (int)v.size() - 1;
        while (v[rr] == "") {
            --rr;
        }
        while (ll <= rr) {
            mm = (ll + rr) / 2;
            while (v[mm] == "") {
                // go left or right, either is OK.
                --mm;
            }
            if (s > v[mm]) {
                ll = mm + 1;
                while (ll <= rr && v[ll] == "") {
                    ++ll;
                }
            } else if (s < v[mm]) {
                rr = mm - 1;
                while (rr >= ll && v[rr] == "") {
                    --rr;
                }
            } else {
                break;
            }
        }
        printf("%d\n", (ll <= rr ? mm : -1));
        
        v.clear();
    }
    
    return 0;
}