计算 s[i] = s[i+1] 的索引数：范围查询

给定一个字符串str 。现在对于由两个整数L和R组成的每个查询，任务是找到索引的数量，使得str[i] = str[i+1]和L ≤ i, i+1 ≤ R 。
例子：

Input: str = “ggggggggggg”, query[] = {{1, 2}, {1, 5}}
Output: 1 4
The answer is 1 for first query and 4 for second query.
The condition is true for all indices except the last one in each query.
Input: str = “geeg”, query[] = {{0, 3}}
Output: 1
The condition is true only for i = 1.

编程需要懂一点英语

方法：创建一个前缀数组pref使得pref[i]保存从1到i-1的所有索引的计数，使得str[i] = str[i+1] 。现在对于每个查询(L, R) ，结果将是pref[r] – pref[l] 。
下面是上述方法的实现：

C++

// C++ program to find substring with 
#include 
using namespace std;
 
// Function to create prefix array
void preCompute(int n, string s, int pref[])
{
    pref[0] = 0;
    for (int i = 1; i < n; i++) {
        pref[i] = pref[i - 1];
        if (s[i - 1] == s[i])
            pref[i]++;
    }
}
 
// Function to return the result of the query
int query(int pref[], int l, int r)
{
    return pref[r] - pref[l];
}
 
// Driver Code
int main()
{
    string s = "ggggggg";
    int n = s.length();
 
    int pref[n];
    preCompute(n, s, pref);
 
    // Query 1
    int l = 1;
    int r = 2;
    cout << query(pref, l, r) << endl;
 
    // Query 2
    l = 1;
    r = 5;
    cout << query(pref, l, r) << endl;
 
    return 0;
}

Java

// Java program to find substring with
 
import java.io.*;
 
class GFG {
 
// Function to create prefix array
static void preCompute(int n, String s, int pref[])
{
    pref[0] = 0;
    for (int i = 1; i < n; i++) {
        pref[i] = pref[i - 1];
        if (s.charAt(i - 1)== s.charAt(i))
            pref[i]++;
    }
}
 
// Function to return the result of the query
static int query(int pref[], int l, int r)
{
    return pref[r] - pref[l];
}
 
// Driver Code
 
    public static void main (String[] args) {
    String s = "ggggggg";
    int n = s.length();
 
    int pref[] = new int[n];
    preCompute(n, s, pref);
 
    // Query 1
    int l = 1;
    int r = 2;
    System.out.println( query(pref, l, r));
 
    // Query 2
    l = 1;
    r = 5;
    System.out.println(query(pref, l, r));
    }
}
// This code is contributed by inder_verma..

Python3

# Python3 program for the given approach
 
# Function to create prefix array
def preCompute(n, s, pref):
  
    for i in range(1,n): 
        pref[i] = pref[i - 1]
        if s[i - 1] == s[i]:
            pref[i] += 1
   
# Function to return the result of the query
def query(pref, l, r):
  
    return pref[r] - pref[l]
   
if __name__ == "__main__":
 
    s = "ggggggg"
    n = len(s)
   
    pref = [0] * n
    preCompute(n, s, pref)
   
    # Query 1
    l = 1
    r = 2
    print(query(pref, l, r))
   
    # Query 2
    l = 1
    r = 5
    print(query(pref, l, r))
     
# This code is contributed by Rituraj Jain

C#

// C# program to find substring with
 
using System;
 
class GFG {
 
 
// Function to create prefix array
static void preCompute(int n, string s, int []pref)
{
    pref[0] = 0;
    for (int i = 1; i < n; i++) {
        pref[i] = pref[i - 1];
        if (s[i - 1]== s[i])
            pref[i]++;
    }
}
 
// Function to return the result of the query
static int query(int []pref, int l, int r)
{
    return pref[r] - pref[l];
}
 
// Driver Code
 
    public static void Main () {
    string s = "ggggggg";
    int n = s.Length;
 
    int []pref = new int[n];
    preCompute(n, s, pref);
 
    // Query 1
    int l = 1;
    int r = 2;
    Console.WriteLine( query(pref, l, r));
 
    // Query 2
    l = 1;
    r = 5;
    Console.WriteLine(query(pref, l, r));
    }
}
// This code is contributed by inder_verma..

PHP

Javascript

输出：

1
4